5. The two numbers $a$ and $b$ both lie between -5 and 10 inclusive. What is the largest possible value of $a-b$ ?
A -5
B 0
C 10
D 15
E 20
5. D The largest possible value of $a-b$ comes from subtracting the smallest possible value of $b$ from the largest possible value of $a$. Hence the largest possible value is
$$
10-(-5)=10+5=15
$$