Explanation

(d) When a single heater (resistance $R_{1} = R$) is connected to 220 V, then it will consume a power $P_{1} =$1000 W. If two such identical heaters are connected in parallel (total resistance $R_{2} = R_{1}/2$ = $R/2)$ to some source, then it will consume power $P_{2}$.
$\frac{P_{2}}{P_{1}} = \frac{R_{1}}{R_{2}}$
$\Rightarrow \ P_{2} = 2P_{1}$
${\ P}_{2} = \ $2000 W