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。

Though it is a          job, he  still devotes much time and energy to it.

poor-paying

poorly-paying

poorly-paid

poor-paid

考查构词法。本题中考查了复合形容词的构词法，“使用副词+过去分词” 构成新的形容词，如“newly-discovered”最新发现的；本句中“poorly-paid报酬极少的”。句意：尽管这是一份报酬极少的工作，但他仍然花了很多时间和精力做它。故选C项。

He punished the children          their carelessness         making them pay for the damage.

by; for

with; by

for; by

about; with

考查介词。句意：他因为孩子们的粗心惩罚他们赔偿损失。根据句意可知：“their carelessness"表示他们被惩罚的原因，需用介词for表原因。"making them pay for the damage"表示他们被惩罚的方式，需用介词by表方式。故选C项。