The host range of a virus is determined by A. whether the glycoproteins or capsid proteins on its surface recognize those of the host cells. B. whether its nucleic acid is DNA or RNA. C. the proteins in the host's cytoplasm. D. the enzymes produced by the virus before it infects the cell E. the enzymes carried by the virus

A. whether the glycoproteins or capsid proteins on its surface recognize those of the host cells.

Explanation:

Virus has different surface proteins that are recognized by the receptors present on its host cell. The range of a virus is determined by the recognition of these proteins by the host cell.

The interaction between the receptor on the host cell and surface proteins on the viral capsid is important for viral genome entry in the host cell and to determine the range of the host cells.

If the surface protein of the virus is not able to bind to the receptor on any cell then the virus can not infect the cell. For example, the HIV virus infects only those cell which have CD4 receptors. So the right answer is A.

the level of progesterone is low at the pre-ovulatory phase of the cycle but it gradually increases and the levels are high at the luteal phase. if pregnancy occurs, the level of progesterone will be high throughout the pregnancy.

if egg is fertilized and the mother gets pregnant, progesterone starts preparing the uterus for the implantation. it starts building up the lining of uterus and make it hostile of the period of pregnancy.