necessary to explain your theory _____, otherwise the audience won’t make sense of what you are trying to get across. A:on purpose B. at length C. at random D. on average; B【解析】试题分析：句意：有必要详细地解释你的理论，否则观众就不会明白你想要表达的意思。 A. on purpose故意地； B:at length详细地； C:at random D:on average;
