当然正确了,
Who's that (speaking)?
不过节电话的时候常用的是下面的
Suddenly,it was quiet for a long time at the other end of the line.Then he asked,"Who is it?Who's speaking?".
突然间,电话的另一端安静了好长一段时间,然后才听到士兵开口问:「是谁在说话?」
Marvell:Hello,this is Marvell,who's that speaking?
马韦尔:喂,我就是,请问您是?