Although it shouldn’t have happened, on a dive i fail to watch my spg and run out of air. if my buddy is close by, my best option is to another option is to if i’m in shallow water and the surface is closer than my buddy.
a ascend using my buddy's alternate air source / make a controlled emergency swimming ascent
b ascend using my buddy's alternate air source / make an buoyant emergency ascent
c make a normal ascent / ascend using my buddy's alternate air source
d make a controlled emergency swimming ascent / make a normal ascent

Uranium has two naturally occurring isotopes. 238u has a natural abundance of 99.3% and 235u has an abundance of 0.7%. it is the rarer 235u that is needed for nuclear reactors. the isotopes are separated by forming uranium hexafluoride uf6, which is a gas, then allowing it to diffuse through a series of porous membranes. 235uf6 has a slightly larger rms speed than 238uf6 and diffuses slightly faster. many repetitions of this procedure gradually separate the two isotopes. what is the ratio of the rms speed of 235uf6 to that of 238uf6? express your answer to five significant figures.