英英语语------you called,i was taking a shower.为什么用when,不用while呢

I was taking a shower in the bathroom when the UFO landed 的意 the alien was buying a cap,i called my friend 用when还是while 为什么taking a shower uses fewwer water than taking a bath里面要用i _______(When/While) I was taking a walk in the park,I met To 英语填空:1.When you called me yesterday.I was still ____ a meeti taking a shower & taking shower “He will look after my bird while I go away"为什么用while不用when I was looking for my key when you called. taking a shower If I were you,I'd sleep after taking a long walk.为什么要用taking _____she was taking walks,it rained A.when B.while C.as I was writing a letter when she called.