语法填空
①Everyone enjoys the life-saving benefits vaccines provide, but they’ll ___________(exist) only as long as everyone shares in the risks.
②If it weren’t for Rachel Carson, the environmental movement might not ___________ today. (exist)
③To people who are used to the limited choice of apples such as Golden Delicious and Royal Gala in supermarkets, it can be quite an eye opener to see the range of classical apples still in _____________, such as Decio which was grown by the Romans. (exist)