Given a scientific question and its correct answer, generate supporting facts for the answer. This supporting fact can be an explanation for the answer to the given question.

[EX Q]: Question: What is the term for land that has permanently frozen soil? Answer: permafrost
[EX A]: Permafrost is land with permanently frozen soil.

[EX Q]: Question: How many types of major tissues do modern plants have? Answer: three
[EX A]: A tissue is a group of specialized cells of the same kind that perform the same function. Modern plants have three major types of tissues. They're called dermal, ground, and vascular tissues.

[EX Q]: Question: What type of charge do electrons have? Answer: negative
[EX A]:
Electrons have negative charge and protons have positive charge. The magnitude of the charge is the same for both, .