The num$1$ and num$2$ variables have the int data type and contain the numbers $13$ and $5,$ respectively. The answer variable has the double data type. Which of the following statements will require an explicit type conversion to evaluate correctly? a$.$ answer $=$ num$1/4\mathrm{.}0$; b$.$ answer $=$ num$1+$ num$1/$ num$2$; c$.$ answer $=$ num$1-$ num$2$; d$.$ none of the above