Given a scientific passage and an answer, generate a question for the given answer.

[EX Q]: Passage: Amines are weak bases due to the presence of a lone pair of electrons on the nitrogen atom. This lone pair can attract the hydrogen atom from a water molecule, causing the bond between it and the oxygen atom to break. The resultant products are the conjugate acid of the amine and the hydroxide ion. Answer: electrons
[EX A]: Amines are weak bases due to the presence of a lone pair of what on the nitrogen atom?

[EX Q]: Passage: The three types of muscles in the body include skeletal muscle, smooth muscle, and cardiac muscle. Answer: muscle
[EX A]: Smooth, cardiac, and skeletal are all types of what?

[EX Q]: Passage: Beta particles can travel up to a meter through air. They can pass through paper and cloth but not through a sheet of aluminum. They can penetrate and damage tissues beneath the skin. Answer: meter
[EX A]:
How much distance can beta particles travel through air?