Genetic Variation Can Arise from Conjugation in Bacteria

Genetic variation can arise from conjugation in bacteria. During conjugation

A) there is no physical contact between the bacteria.
B) a bacteriophage acts as a vector for DNA.
C) the incoming DNA is always broken down by enzymes in the recipient bacteria.
D) the incoming DNA may be integrated into DNA in the recipient bacteria or may be maintained as an independent plasmid.
E) small pieces of DNA are transferred from one bacteria to another through bacterial pili.