Which of the following is not used as cooking fuel?

(A) LPG

(B) Biogas

(C) CNG

(D) Coal

Observer A is on Earth looking at the Moon, and observer B is on the Moon looking at Earth.

Which of the following quantities do the observers agree on for the Earth-Moon system?

Check all that apply.

Which of the following below is the light behavior which best matches the behavior of a sound wave when we hear an echo?

a) pencil looking bent in a glass of water
b) A person looking in the mirror
c) Light waves bending when the move from the air into the water
d) A light wave heating a roof.

Which of the following is not equal to 1 mm?