Demo: BPL/G

The correct answer is: 2 tethers at 10 m each or 1 tether at 20 m. These lengths ensure safe anchoring of the balloon. The other options are either too short or too long, which could compromise safety.

The correct answer is that hydrogen may self-ignite and burn with an invisible flame. Hydrogen burns with an almost invisible flame. The other options are wrong: hydrogen does not poison air, does not burn with a bright flame, and does not collect in the basket to cause breath shortness.

Embedded steel threads (filaments) provide conductivity because steel conducts electricity. Surface painting, impregnation, or plastic tape do not make the ropes conductive, as these materials are insulators or non-conductive.

The inclination is lowest at the magnetic equator because the Earth's magnetic field lines are parallel to the surface there. At the magnetic and geographic poles, inclination is highest. At the geographic equator, it is not necessarily zero.

Electronic devices create magnetic fields that can disturb the direct reading compass. Artificial horizon, turn coordinator, and airspeed indicator do not rely on magnetism and are not affected.

The Earth's rotational axis runs through the geographic North and South Poles, as these are the true rotation points. The magnetic poles are offset and move over time, so they are not the axis points.

Correct: The polar axis of the Earth crosses the geographic South Pole and the geographic North Pole and is perpendicular to the plane of the equator. The Earth's axis passes through the geographic, not magnetic, poles and is perpendicular to the equator. Other answers confuse poles or give wrong angles.

The shortest distance between two points on Earth is always along a great circle. Small circles, rhumb lines, and parallels of latitude are longer or follow different paths, so they are not the shortest route.

The correct answer is '21,600 NM.' because 1 degree of latitude equals 60 NM and the equator is 360 degrees (360 × 60 = 21,600 NM). '40,000 NM.' and '10,800 km.' are too large or too small, '12,800 km.' is also too low.

The polar circles are each 23.5° from the North and South Poles. This is correct due to Earth's axial tilt. The other options are incorrect because they use wrong latitudes or reference points.

One degree of latitude equals 60 NM because 1 degree along a meridian always measures about 60 nautical miles. 1 NM, 60 km, and 30 NM are incorrect as they do not match the true distance of one degree of latitude.

1 degree of latitude equals 60 NM. 240 NM equals 4°. Adding 4° to 47°50'27''N gives 51°50'27''N. The other options are either too far north, too far south, or too close to the starting point.

The correct answer is 60 NM because one degree of longitude at the equator equals exactly 60 nautical miles. The other options are too large and do not match the definition of a nautical mile, which is 1/60 of a degree at the equator.

The Earth rotates 360° in 24 hours. For 20°, it takes 1 hour 20 minutes. The other answers are incorrect as they are either too short or too long. 1:20 h is correct because 20° × 4 minutes = 80 minutes = 1:20 h.

The correct answer is 0:40 h because the Earth rotates 360° in 24 hours, so 1° equals 4 minutes. Therefore, 10° equals 40 minutes. The other answers are incorrect as they are either too much, too little, or far too little time.

1600 CEST is two hours ahead of UTC. So, 1600 CEST equals 1400 UTC. The other answers are incorrect because they do not account for the two-hour time difference.

The correct answer is '1600 UTC.' CET is one hour ahead of UTC, so you subtract one hour. The other answers are incorrect because they subtract too much, too little, or do not convert at all.

Civil twilight is the period before sunrise or after sunset when the sun's center is 6 degrees or less below the true horizon. The other answers are incorrect because they mention 12 degrees or the apparent horizon, which is not the correct definition.

The true course (TC) is the angle between true north and the course line. Magnetic north relates to magnetic course, and directions to the poles are not course definitions.

Correct: a line connecting all points with the same variation. Variation is the angle between true and magnetic north. The other options are incorrect: deviation, inclination, and heading refer to different navigation concepts.

In aeronautical navigation, nautical miles (NM) and kilometers (km) are used for horizontal distances because they are internationally standardized. Land miles, yards, meters, feet, and inches are not standard for this purpose.

1,000 feet equal about 300 meters, since 1 foot is about 0.3048 meters. 30 meters and 3,000 meters are too little or too much, and 30 kilometers is far too much. Only 300 meters is correct.

'Knowledge' is correct because understanding aviation principles, regulations, and procedures is part of knowledge. 'Skills' are about practical execution, 'Attitudes' are about mindset, and 'Experience' is about accumulated practice.