Mable had an advantage over her classmates in ----- she had

Mable胜过她的同学、因为她对十分外国文学十分熟悉.
in that是因为的意思.再比如：This book is different from that book in that this one is about chemistry and that one about history.这本书不同于那本,因为这本是有关化学的,而那本是有关历史的.in that引导原因状语从句.