If / else

Conditionals let a program choose a path. Only the first matching branch runs.

`if` runs its block when the condition is True; `elif` adds more cases; `else` catches the rest. Indentation (4 spaces) marks what is inside.

score = 82
if score >= 90:
    print("A")
elif score >= 80:
    print("B")
else:
    print("C")