√x< 4 a.20 b.12 c.2 d.-1 e.5. f. no solution

We know that for √x to be meaningful, we must have x ≥ 0.

If we square both sides of the inequality, we have
  x < 4²
  x < 16

Thus the whole solution is
  0 ≤ x < 16

The following choices are valid solutions to the inequality:
  B. 12
  C. 2
  E. 5

Main idea on left, details on right