If the Efficiency of a Carnot Engine Were to Be $100 \%$

Multiple Choice

If the efficiency of a Carnot engine were to be $100 \%$ , the heat sink would have to be

A) at $100 ^ { \circ } \mathrm { C }$ .
B) at $0 ^ { \circ } \mathrm { C }$ .
C) infinitely hot.
D) at absolute zero.