Why is it critical all winds blow in the same direction tropical storm?

It is critical for all levels of wind to blow in the same direction and speed to be able to force the air up from the surface of the ocean. If the lower winds were blowing in a different direction then the upper winds the winds would not have enough force to push it off the ocean's surface .

Hope this helps?

When all the levels blow in the same direction to form a tropical storm, it creates the critical situation to develop a tropical storm. The strong vertical shear may prevent the storm to rise to its full potential and causes the spreading of energy over too large area. It prevents the storm to strengthen.

a and b because with the other three, they simplify to something else.

a. i. only is correct.