What prevents multiple sperm from fertilizing an egg?

Idon’t understand this can someone give me the answer? you

Paleontologists have found plant fossils deep within the layers of the north polar region. these leaf fossils have been labeled as to the rock layers they were found in, with the lower numbers being layers close to the earth's surface and higher numbers representing deeper layers. according to the numbers of these four leaf fossils, what might you infer?

Viruses have a core made up of everything listed here except a. plasmids. b. genetic material. c. dna. d. rna.