Tick (✓) the correct answer

(d) 17

Let the three consecutive integers be $x, x+1$ and $x+2$.

Equation $=x+x+1+x+2=51$

$\Rightarrow 3 x+3=51$

$\Rightarrow 3 x=51-3$

$\Rightarrow 3 x=48$

$\Rightarrow x=\frac{48}{3}=16$

Middle integer $=x+1=16+1=17$