16) C

Substitute the values given in the options into the inequalities.

A – Wrong
When x = -1, and y = -6
y ≥ x² + 3
-6 ≥ -1² + 3
-6 ≥ 1 + 3
-6 ≥ 4
This is definitely wrong.

B – Wrong
When x = 2, and y = -1
y ≥ x² + 3
-1 ≥ 2² + 3
-1 ≥ 4 + 3
-1 ≥ 7
This is definitely wrong.

C – Correct
When x = 1, and y = 6
y ≥ x² + 3
6 ≥ 1² + 3
6 ≥ 1 + 3
6 ≥ 4
This is definitely correct. However, we also need to ensure whether the values can be substituted into the second inequality or not.

x ≥ 1/y

1 ≥ ¹⁄₆

This is also correct. Hence C is the answer. 

D – Wrong
When x = 2, and y = 2
y ≥ x² + 3
2 ≥ 2² + 3
2 ≥ 4 + 3
2 ≥ 7

This is definitely wrong.