14. In a DNA double helix the bases are held together by hydrogen bonds. These hydrogen bonds are (A) covalent bonds (B) non-covalent bonds (C) ionic bonds (D) van der Waals forces

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.

14. In a DNA double helix the bases are held together by hydrogen bonds. These hydrogen bonds are
(A) covalent bonds
(B) non-covalent bonds
(C) ionic bonds
(D) van der Waals forces

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