Correct option is A. True
$$7.5$$ litres $$: 15$$ litres $$=15$$ children $$:30$$ children
We have, $$7.5:15=\dfrac{7.5}{15}=\dfrac{2.5}{5}$$
$$=\dfrac{2.5}{5\times 10}=\dfrac{25}{50}=\dfrac{1}{2}$$
And $$15:30=\dfrac{15}{30}=\dfrac{1}{2}$$
$$\therefore 7.5:15=15:30$$
So, teh given statement is true.