D
本句的意思是：“即使研究有了新的发展，只有一小部分的试验可以不用动物”。因此答案为D。variety和plenty分别表示“多样”和“大量的”，意思不合适。amount后只能接不可数名词，而test是可数名词。
Thejudgewhowas________tohisfavoritewascriticizedbymanypeople.
—Why didn ’t you buy a new car?
—I would have bought one if I _______ enough money.
They________extensiveandpossiblydangerousactualflighttraining.
OneofthedisadvantagesintheGrammar-TranslationMethodisthatthetextsaretakenfrom_____,thelanguageofwhichdoesn'toftenmeetthepracticalneedsofthelearners.