Ans: D
Note that the shaded region represents the solution of
Note that the shaded region represents the solution of
$\left\{ \begin{array}{l}
y \le x +5 \\
x +2y \ge 10 \\
x \le 4
\end{array} \right.$.
I is true. By the third inequality, $a \le 4$.
II is true. By the first inequality, we have
$\begin{array}{rcl}
b & \le & a + 5 \\
a & \ge & b – 5
\end{array}$
III is true. By the second inequality, we have
$\begin{array}{rcl}
a+2b & \ge & 10 \\
a & \ge & 10 – 2b
\end{array}$
