Given a scientific question, generate a correct answer to it.

[EX Q]: What are groups of tens to hundreds of thousands of stars held tightly together by gravity called?
[EX A]: globular clusters

[EX Q]: In the past, what colliding with planet earth has caused many organisms to die off?
[EX A]: asteroids

[EX Q]: What state of matter has a definite volume, but not a definite shape?
[EX A]:
liquid