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

[EX Q]: The newest, outer layers of secondary xylem are called sapwood.
[EX A]: What are the newest, outer layers of secondary xylem called?

[EX Q]: Monatomic ions form when a single atom gains or loses electrons.
[EX A]: What form when a single atom gains or loses electrons?

[EX Q]: A(n) radioisotopes is an isotope that is radioactive.
[EX A]:
What is an isotope that is radioactive called?