Nonzero real numbers x, y, a, and b satisfy x<a and y<b. How many of the following inequalities must be true?
\begin{aligned}
\text { (I) } x+y<a+b
\end{aligned}
\begin{aligned}
\text { (II) } x-y<a-b
\end{aligned}
\begin{aligned}
\text { (III) } x y<a b
\end{aligned}
\begin{aligned}
\text { (IV) } \dfrac{x}{y}<\dfrac{a}{b}
\end{aligned}
Answer Choices
A. 0
B. 1
C. 2
D. 3
E. 4