It was not until 1920 ___ regular radio broadcasts began.

when

which

that

since

此题考查强调句。句意为：直到1920年，常规的电台才开始。这句话把it is/was和that去掉后，仍是完整的一句话，因此我们可以知道这是一个强调句，而且是对not...until“直到...才”的强调。结构是：it is/was+not until+其他成分。故选:C.

Based on the agreement,all payments          be made by the end of the month.

may

can

shall

will

考查情态动词。句意：根据协议，所有款项应在月底付清。shall用于法律，条款中表示必须要做的事。故选C项。

I thought we'd be late for the concert,           we ended up getting there ahead of time.

but

or

so

for

考查连词。句意：我以为我们音乐会迟到了，但是我们提前到达了那里。but 但是；or 或者；so 因此；for因为；两个分句在意义上bu是转折关系，故用but。故选A项。

I can't tell you         way to the Wilson's because we don't have        Wilson here in the village.

a; /

the; a

a; the

the; /

考查冠词。句意：我无法告诉你去威尔逊的路，因为我们村没有一个叫威尔逊的人。the way to...去.....的路，这里是特指去威尔逊家的路，用定冠词the,排除A、C;第二空泛指一个叫威尔逊的人，应该

用不定冠词，a Wilson 一个叫威尔逊的人，排除D项。故选B项。

Small sailboats can easily turn over in the water ________.

if not managed carefully

if are not managed carefully

unless not managed carefully

unless are not managed carefully