<Ul> <Li> Acid phosphatase test for semen </Li> <Li> Cobalt thiocyanate test for cocaine </Li> <Li> Duquenois - Levine reagent for marijuana </Li> <Li> Kastle - Meyer test for blood </Li> <Li> Malachite green test for blood </Li> <Li> Marquis reagent for narcotics </Li> <Li> Benzidine test for blood which changes from clear to blue in color with the presence of blood </Li> </Ul> <Li> Acid phosphatase test for semen </Li> <Li> Cobalt thiocyanate test for cocaine </Li> <Li> Duquenois - Levine reagent for marijuana </Li>

What is considered a positive reaction in the presumptive test