AFSCs range from officer specialties such as pilot, combat systems officer, missile launch officer, intelligence officer, aircraft maintenance officer, judge advocate general (JAG), medical doctor, nurse or other fields, to various enlisted specialties. The latter range from flight combat operations such as a gunner, to working in a dining facility to ensure that members are properly fed. There are additional occupational fields such as computer specialties, mechanic specialties, enlisted aircrew, communication systems, cyberspace operations, avionics technicians, medical specialties, civil engineering, public affairs, hospitality, law, drug counseling, mail operations, security forces, and search and rescue specialties.
What is one of the many types of AFSC employed by the USAF? 
missile launch officer

The majority of studies indicate antibiotics do interfere with contraceptive pills, such as clinical studies that suggest the failure rate of contraceptive pills caused by antibiotics is very low (about 1%). In cases where antibacterials have been suggested to affect the efficiency of birth control pills, such as for the broad-spectrum antibacterial rifampicin, these cases may be due to an increase in the activities of hepatic liver enzymes' causing increased breakdown of the pill's active ingredients. Effects on the intestinal flora, which might result in reduced absorption of estrogens in the colon, have also been suggested, but such suggestions have been inconclusive and controversial. Clinicians have recommended that extra contraceptive measures be applied during therapies using antibacterials that are suspected to interact with oral contraceptives.
What percent is the  failure rate of contraceptive pills?
about 1%

Essential genes are the set of genes thought to be critical for an organism's survival. This definition assumes the abundant availability of all relevant nutrients and the absence of environmental stress. Only a small portion of an organism's genes are essential. In bacteria, an estimated 250–400 genes are essential for Escherichia coli and Bacillus subtilis, which is less than 10% of their genes. Half of these genes are orthologs in both organisms and are largely involved in protein synthesis. In the budding yeast Saccharomyces cerevisiae the number of essential genes is slightly higher, at 1000 genes (~20% of their genes). Although the number is more difficult to measure in higher eukaryotes, mice and humans are estimated to have around 2000 essential genes (~10% of their genes).
What does the definition of essential genes assume an absence of?
environmental stress