Which of these choices demonstrates the significance of the troposphere? Select one:

a. It holds the ozone layer, the blanket of air that keeps ultraviolet light out of the lower levels of the atmosphere.

b. It is the layer furthest from earth and gives way to the depths of space.

c. It contains the air we breathe, which is a mix of mostly nitrogen, oxygen and carbon dioxide.

d. It holds some of Earth's satellites, along with the International Space Station.
SCIENCE NOT PHYSICS!!!

Given the position vector of the particle r(t)=(t+1)i+(t^2−1)j+2t k, find the particle's velocity and acceleration vectors at t=1

Find the magnetic field a distance r from the center of a long wire that has radius a and carries a uniform current per unit area j in the positive z direction.

Ametal ring 4.20 cm in diameter is placed between the north and south poles of large magnets with the plane of its area perpendicular to the magnetic field. these magnets produce an initial uniform field of 1.12 t between them but are gradually pulled apart, causing this field to remain uniform but decrease steadily at 0.240 t/s . (a) what is the magnitude of the electric field induced in the ring? (b) in which direction (clockwise or counterclockwise) does the current flow as viewed by someone on the south pole of the magnet?