_______ is a good nuclear fuel?

A solid metal ball has a spherical cavity. If the ball is heated, the volume of the cavity will_____?

The carbon filament is invented by_____?

To hear a clear echo, the minimum distance should be______?

The centripetal force required for a car or a bicycle to go round a circular curve depends on___?

The lines of force of a uniform magnetic field____?

A cyclotron can accelerate___?

Principal focus of a spherical mirror is between____?

Who was the inventor of positron?

Who invented air conditioning?

The image form by an object of a compound microscope is ?