Competent cells are cells that:.a. can take up DNA from their surrounding environment and integrate it into their own chromosomes by recombination. b. have the ability to produce capsules. c. are killed by heat. d. are also considered "rough-strain" based on colony phenotype.

A) They can take-up DNA from their surrounding environment and integrate it into their own chromosomes by recombination. (Option A)

Explanation:

Competent cells contain altered cell walls which help the DNA to easily pass through it. Some cells need to be exposed to some electrical, or chemical treatments, so, they can transform them into competent cells.

This process is mostly used to introduce recombinant Plasmid DNA into competent cells. This process only requires DNA in the surrounding environment and does not require a donor cell. Two methods are using for preparation of competent cell:

1) Natural competence: Take-up DNA from their surrounding environment by the transformation.

2) Artificial competence: The stranded method for the preparation of these cells are treated with calcium ions.

c. heat from the poles back down towards the equator.