这个系列的电脑非常快，但它们的后继者将会更快。

This range of computers is very fast, but their ___successors will be even faster.

汽车的自然后继者在七十年代末首次被构想出来，但由于控制系统计算能力不足，双模式车辆从未被制造出来。

The natural ___successor of the car was first thought of in the late seventies, but due to lack of computing power for the control systems, the dual mode vehicle was never made.

该公司的新智能手机是去年畅销型号的直接后继者。

The company's new smartphone is the direct ___successor to last year's best-selling model.