If only I _________ how to operate a computer!

A．learn

B．would learn

C．have learned

D．had learned

A．learn

B．would learn

C．have learned

D．had learned

A．had known

B．would know

C．should know

D．knew

A．had known

B．would know

C．should know

D．knew

A．How to send an E-mail.

B．How to operate a computer.

C．How to run the spell checker.

D．How to copy sentences and paste them in other places.

A．The development of electronic computer.

B．How to operate a computer?

C．What's the use of computers?

D．What do the scientists and technicians do about computers?

A．It is performed by a computer-designed high precision device.

B．Surgeons wear virtual reality helmets to receive feedback provided by a computer.

C．Surgeons move robotic instruments by means of a computer linked to them.

D．A 3-D image records the movements of the surgeons during the operation.

A．It is performed by a computer-designed high precision device.

B．Surgeons wear virtual reality helmets to receive feedback provided by a computer.

C．Surgeons move robotic instruments by means of a computer linked to them.

D．A 3-D image records the movements of the surgeons during the operation.

A．How to operate the computer.

B．How to have a break after work.

C．How to choose the right glasses.

D．How to avoid eye problems before computer.