Turn the given fact into a question by a simple rearrangement of words. This typically involves replacing some part of the given fact with a WH word. For example, replacing the subject of the provided fact with the word "what" can form a valid question. Don't be creative! You just need to rearrange the words to turn the fact into a question - easy! Don't just randomly remove a word from the given fact to form a question. Remember that your question must evaluate scientific understanding. Pick a word or a phrase in the given fact to be the correct answer, then make the rest of the question. You can also form a question without any WH words. For example, "A radio converts electricity into?"

Fact: Vaccination leads to immunity and extremely rarely with serious side effects.
What leads to immunity and extremely rarely with serious side effects?

Fact: Electrical currents can cause objects to repel each other.
Which of the following can cause objects to repel each other?

Fact: the smallest agents of disease are not cells.

what are not cells?