Why am i coughing up blood but im not sick?

The purity of ecstasy is always in question, why? (short answer)

Select all of the possible methods of aids transmission.

When a researcher debriefs her participants, she: provides a detailed explanation of the study. removes their undergarments. tells them they can stop taking part at any time. provides an detailed explanation of the study, and tells them they can stop taking part at any time.