Backup of sewage in the preparation area or a serious pest infestation are hazards or contaminants that are grounds for immediate closure of an operation. A sewer drain backup may be among the most unpleasant experiences one can get as a house owner.
Answer - A
Semi-conservative model of replication involves the replication of DNA in all the familiar cells in such a way that each newly synthesized daughter cell contains a double helix with one new strand and one old strand.
The answer is the first one