What does not have to happen in order for a pregnancy to occur?

menstruation
implantation
fertilization
ovulation

Astudy shows that an influenza vaccine is 71.4% effective in preventing a particular type of influenza. if 15,422 people receive the vaccine, how many would not be protected and would be likely to get infulenza?

Marijuana is an example of a(n) drug

What causes fermentation a. antibodies b. antigens c. microorganisms d. antibiotics