Which statement about the prevention and treatment of hiv/aids is true? a. it is no longer necessary to screen voluntary blood donors for hiv/aids because the storage process kills the virus in the blood. b. one cost-effective measure to reduce maternal-to-child transmission of hiv is to avoid unwanted pregnancies of hiv-positive women through contraception. c. people with hiv are started on treatment when their cd4 count drops to 200, according to the latest who guidelines. d. needle exchange programs for injecting drug users have not shown much success in reducing the incidence of hiv infection.