Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

The human body has as many as two trillion lymphocytes, and lymphocytes make up about 25% of all of leukocytes.
The human body has as many as two trillion lymphocytes, and lymphocytes make up about 25% of all of what?

Mercury is the name of the smallest planet in our solar system, which is also nearest to the sun.
What is the name of the smallest planet in our solar system, which is also nearest to the sun?

Stringed instruments can help show the relationship between tension and frequencies in strings.

Stringed instruments can help show the relationship between tension and what in strings?