What letter represents the trough? :) PLEASE FAST!

1) A
2) B
3) C
4) D

What happens to the atomic radius when an elctron is lost

How would the number of moles (n) of o2 change if the atmospheric pressure doubled but all other variables stayed the same

Great amounts of electromagnetic energy from our sun and other bodies in space travel through space. which is a logical conclusion about these electromagnetic waves? their energy must be very their frequency must be very low these waves can travel without a medium they only travel through a vacuum of space