Which gland secretes thyroxine? a. hypothalamus b. pituitary gland c. thyroid gland d. adrenal gland

It is the thyroid gland that secretes thyroxine  , think of the beginning of it and how it is the same as the gland it is secreted from 

Crossing over creates new combinations of genes in the gametes that are not found in either parent contributing to genetic diversity

When a virus infects a host cell, it uses the cell's machinery to make copies of its own genetic material in a process called replication. finally, during the process of self-assembly, that protein shell and the copies of the virus's genetic material are assembled into new viruses.