Question

As the sea ice melts sooner each swimmer,polar bears are forced to come ashore earlier and face food shortages _____ they have stored enough fat to last them through the season.

A．before

B．unless

C．since

D．until

Answer 1

A

本題考查連詞。句意：因為海冰融化得比游泳者早，北極熊沒來得及為整季儲存足夠的脂肪，就被迫提前上岸，面臨食物短缺。before conj.在……之前；比……早些。