Please help with a simple Physics question! Regions of compression and rarefaction help define .

a. electromagnetic waves
b. longitudinal waves, but not transverse waves
c. transverse waves, but not longitudinal waves
d. all mechanical waves

SERIOUS ANSWERS PLEASE, THANK YOU AND GOD BLESS

Consider a u-tube whose arms are open to the atmosphere. now equal volumes of water and light oil (ρ = 49.3 lbm/ft3) are poured from different arms. a person blows from the oil side of the u-tube until the contact surface of the two fluids moves to the bottom of the u-tube, and therefore, the liquid levels in the two arms are the same. if the fluid height in each arm is 30 in, determine the gage pressure exerted by the person on the oil by blowing.