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。
_______foralongtime,mostofthecropsinthisareadiedfromlackingwater.
_______thefirstlanguageisusedintheteachingofthesecondlanguageintheGrammar-TranslationMethod.
________, what could we do?
Hehasdeeploveforthepeopleand________loyaltytothecountry.
In our department, every student _________ after-school activities.
