问题
选择题
Was it because of the heavy snowstorm in Europe ________ the flight had to be put off？
A．which
B．so
C．why
D．that
答案
Ｄ
考察强调句型。It is/was被强调成分that/who其他成分；这是强调句型的基本结构。本题强调的是介词短语because of the heavy snowstorm in Europe。故D正确。