What does plasmid stability mean in a competent host?

Correct answer: Plasmid remains maintained in host

The direct answer is D: plasmid remains maintained in the host. A plasmid is a small, usually circular DNA molecule that is separate from the main chromosome and can carry a useful gene. In a competent host, stability means that after the plasmid enters the cell, it is copied or retained and passed to daughter cells instead of being rapidly lost. The reasoning is: plasmid enters the host; the host keeps it; the plasmid is replicated or distributed during cell division; therefore the plasmid remains present. Selection pressure, such as an antibiotic, gives plasmid-containing cells a growth advantage and helps remove cells that have lost the plasmid, although stability also depends on the vector and host. Option A is wrong because a plasmid is DNA, not water. Option B is the opposite of stability: constant disappearance means instability. Option C is wrong because plasmids do not digest proteins; they may carry genes that encode proteins. Option D is correct because maintenance in the host is exactly the meaning of plasmid stability. Memory cue: stable plasmid means “stays inside and is retained.”