The failure, till now, to produce an effective aids vaccine may be due to the fact that the causative agent mutates continuously thus it is practically impossible for the body immune system to take advantage of vaccination.

a. true. b. false

A. True.

Explanation:

The AIDS virus may constantly change it's form in the host body by mutating. The body immune system becomes unable to produce antibodies which can fight against these mutated cells.

Also, the vaccination used for the purpose of immunization will not be able to combat will the causative agent in the body of the host. As the vaccine contains the microbe which can fight against the virus present in the body. But as the virus is changing it's form the microbe may not be able to compete with the virus. Hence, the use of vaccine will become useless.

c

explanation:

the supermassive black hole is in the middle of the galaxy.