Which of the following statements is correct about black holes?
black holes cannot be seen because light cannot escape from them.
black holes will produce new stars.
a black hole is the beginning of a star’s life cycle.
black holes are stars that are too bright to be seen safely.

Based on the observation that only male crickets produce a song, you hypothesize that a male's song is a form of communication to potential mates. you set up a simple experiment to test this hypothesis. in the laboratory, you place a male snowy tree cricket in enclosure a, which is adjacent to enclosureb. in enclosure b, you place other insects, one at a time, and observe their responses to the male's song. the enclosures are designed so that the two insects being tested cannot see or smell each other, but sound is transmitted from enclosure a to enclosureb.