You are presented with the quiz "Objects that are a few nanometers in size can be seen only with:" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "viruses are so small that they can be seen only with an electron microscope" and "viruses Viruses are very small, a few nanometers in size". 

So, what's the best answer to the question?


 

 an electron microscope          