28. The firm invested approximately 60 million dollars in________it says is the world’s largest bottle-bottle recycling plant.

A．that

B．where

C．what

D．How

带式输送机中的绞车式拉紧装置是( )装置。

A．手工操作

B．自动拉紧

C．车式拉紧

D．垂直拉紧