A maglev is a type of train that rides on a "cushion of magnetism." These trains can attain very high speeds because
A. friction is greatly reduced.
B. gravity is reduced on the track.
C. the magnetic field of the maglev train is stronger than the magnetic field of the track.
D. the magnetic field of the track is stronger than the magnetic field of the maglev train.

A. friction is greatly reduced.

Explanation:

Maglev train runs on the principle of repulsion force due to magnetic field

here we know that magnetic field will apply force on the train which helps to levitate train in air

This is why it runs forward due to other component of magnetic force and hence it can run with high speed in air with least friction as there is no two surfaces in contact with each other

So here we can say that

Train run with very high speed due to least value of friction between two surfaces which moves relative to each other

so correct answer is

A. friction is greatly reduced.

answer: the exterior temperature of commercial jet planes as they leave the stratosphere and return to the ground increases steadily.

explanation:

the lower most layer of atmosphere is troposphere which extends from 0 to 12 km above the surface of the earth. the temperature initially decreases as distance is increased from the earth's surface. commercial jets fly in lower part of the stratosphere. the stratosphere extends upto 50 km. the temperature in stratosphere starts rising again due to presence of ozone which traps the uv rays.

thus, when the planes leave the stratosphere and return to the ground, the exterior temperature increases steadily.