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.

According to Professor Johnson, we don't have to read the book if we don't want to, as it is              .

worthwhile

necessary

optional

serious

考查形容词词义辨析。句意：根据约翰逊教授的说法，如果我们不想读这本书，就不必读，因为它是可选择的。A. worthwhile值得的； B. necessary 必要的；C. optional 可选择的；D. serious 严肃的，认真的。根据“  we don't have to read the book if we don't want to”可知，这本书读不读都可以，由此可知它是“可选择的”。故选C项。

         Jixi today is more beautiful now. Mr.Jakson said he would visit it         third time.

The; /

The; the

/; a

The; a

考查冠词。句意：今天的鸡西市更漂亮了。Jakson先生说他将又一次来到这里。第一空“鸡西市”应用定冠词；第二空“不定冠词a/an+序数词+名词” 强调在已知数量上在累加一个，且 third为辅音音素开头的单词，应用a。故选D项。

Don’t mention that at the beginning of the story, or it may             the  shocking end.

give out

give away

give up

give off

考查动词短语辨析。句意：不要在故事的开头提到它，否则会泄露令人震惊的结局。A. give out分发；B. give away泄露；C.give up 放弃；D. give off发出（光），根据“the shocking end”可知，此处表示“泄露”。故选B项。

All we need          a piece of advice on how we can improve our time management.

are

is

were

was

考查be动词和时态。句意：我们需要的只是一条关于如何改进时间管理的建议。分析句子可知，说明一般情况应该用一般现在时，这句话的主语是All we need, 所以为主语从句，当主语从句作主语时，谓语动词用单数，所以用is。故选B项。