How can an auxotrophic strain help in safety?

Correct answer: Survival in outside environment may be reduced

An auxotrophic strain has a metabolic deficiency and cannot synthesize a nutrient or compound that its parent strain can normally make. It therefore requires a supplemented laboratory medium for efficient growth. The governing safety concept is biological containment: if the strain escapes into an environment lacking the required supplement, its growth and long-term survival may be reduced. Thus option A is correct, although auxotrophy is a risk-reduction measure rather than an absolute guarantee of containment. It does not mean that DNA uptake becomes impossible, that the host is always stronger, or that a marker is necessarily absent. Environmental conditions and possible compensating mutations must also be considered.