问题
选择题
Scientists have created GM tomatoes which ______ fresh for 45 days, three times as long as normal tomatoes.
A．are stayed
B．have been stayed
C．stay
D．stayed
答案
答案：C
考查时态。which引导的定语从句是说明转基因西红柿的一般性质，故用一般现在时；又因为stay是连系动词，故选C。