The machine ______, the next step was how to operate it. A: having been installed B: B．had been installed C: having being installed D: has been installed

The machine ______, the next step was how to operate it. A: having been installed B: had been installed C: having being installed D: has been installed

Why is the platform of the warehouse installed with a dock-leveler? It is installed with a dock-leveler to have smooth cargo ____ ____ ____.

A set of are installed to control

They are going to have the serviceman______an electric fan in the officetomorrow.(1998.1.CET-4) A: install B: to install C: to be installed D: installed

They are going to have the serviceman ________ an air-conditioner in the office next week. A: install B: to install C: to be installed D: installed

Once installed, this heater operates____________.

It's terribly hot in the office; we're going to have an air-conditioner ______ tomorrow. A: to install B: install C: to be installed D: installed

如果安装了新组件，则可以继续操作。 A: If a new component is installed, you can continue the operation. B: In the event that a new component is installed, you can continue operation. C: Provided a new component is installed, you can continue operation. D: Providing a new component is installed, you can continue operation.

Fusible plugs are installed in fire-tube boilers to （）.