Why do some animal viruses have an external envelope, while bacteriophages never do?
A. When animal cells are lysed, part of the plasma membrane attaches to the virus; in bacterial cells, it is covered by the cell wall.
B. Some animal viruses bud out, taking part of the plasma membrane with them, whereas phages always lyse the host bacterial cell when they exit.
C. When phages bud out of the host bacterial cell, they take with them part of the cell wall which forms the capsid, not an envelope.
D. When bacteriophages bud out, the plasma membrane is beneath the cell wall and therefore cannot be removed.
Answer: B
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