重點(diǎn)講解：
1. add to
添加；增加；摻加；
eg. A few jokes add leaven to a boring speech.
幾句笑話可給枯燥無味的演講增添活躍的氣氛。
eg. Her comments will add to the uncertainty of the situation.
她的批評將會使局勢更加不穩(wěn)定。
2. be confined to
受限制的；被限定；
eg. The problem is not confined to Germany.
問題不僅限于德國。
eg. These dangers are not confined to smokers.
這些危險(xiǎn)不只是困擾吸煙者。
3. threnten to do sth.
（壞事）可能發(fā)生，將要發(fā)生；
eg. Such measures threaten to provoke escalating retaliation and a full-blown trade war.
這些措施將招致更大規(guī)模的貿(mào)易報(bào)復(fù)措施，甚至全面的貿(mào)易戰(zhàn)。
eg. He can even threaten to call the deal off.
他甚至還可以威脅要取消這筆交易。