27. Which of the followings is an example of a silent mutation? (A) UAC to UAG (B) UCC to UCA (C) AAA to UAA (D) UAA to UGA

5. Which of the following statements is INCORRECT for retroviruses? (A) They are enveloped RNA virus. (B) They encode reverse transcriptase and replicate through a DNA intermediate. (C) Some of them produce tumors in the infected animals. (D) Retroviruses include human immunodeficiency virus (HIV) which primarily infects CD8 T cells.