Many ways have been found______small and simple machine to process large and complicated m

______ many times, this radio receiver is found very sensitive.A．Being testedB．Having been

How many shoes ___ this year？A、have been producedB、were producedC、produced

In recent years there has been a ______ increase in the cost of living; many families have

Now many farmers have reverted to traditional farming methods, ______ their ancestors way

Scientists have found that the way the brain works is _____ complicated than they ha

Up to now there have been many explanations _____