You test a strain of bacteria, Strain X with an antibiotic and all of the bacteria are killed. Overnight there is an accident and your bacteria strain is mixed with another strain, Strain Y, known to be antibiotic resistant. You separate them out
again and perform the same antibiotic test on Strain X again, but this time a few survive. What probably happened?
A. Mixing with the other strain dissolved the capsule on some of the bacteria, allowing them to survive.
B. Bacteria can't transfer anything to each other, it was a coincidence.
C. When they mixed, some of the bacteria from strain X obtained plasmids from strain Y, these plasmids gave them DNA that allowed
them to resist the antibiotic.
D. Some of the bacteria from strain X engulfed the strain Y bacteria, taking their resistance to antibiotics.

C. When they mixed, some of the bacteria from strain X obtained plasmids from strain Y, these plasmids gave them DNA that allowed  them to resist the antibiotic.

Explanation:

Conjugation is a mode of sexual reproduction used by some strains of bacteria to reproduce. In this the bacteria transfers the genetic material to another bacteria through direct contact. In this one bacteria act as a donor and another one act as a recipient.

The strain X which was affected by the antibiotic might have mixed with the strain Y, as a result of this strain X being not resistant with the antibiotic died. But when this bacterial strain got mixed with the strain Y, which is antibiotic resistant. The strain X might received the antibiotic resistant property from strain Y through sexual reproduction by the mode of conjugation. In this plasmid DNA transfer from strain Y to strain X, helped strain X to develop antibiotic resistance, and further helped strain X to survive.