batch file nested if statment crashes

Question

I am trying to learn batch by writing simple programs, but I had a problem that is completely stopping me. I figured out that it kept crashing on the nested if statements, but as soon as I removed the nested part, it worked fine.

set questionNumber=1
if %questionNumber%==1 (
    set /p answer=Test?
    if %answer%==yes (
        echo hi
    )
)
pause>nul

Answer 1

setlocal enableDelayedExpansion
set questionNumber=1
if %questionNumber%==1 (
    set /p answer=Test?
    if !answer!==yes (
        echo hi
    )
)
pause>nul

Delayed expansion