GWD31 6-13 跪求指点

Q13:

Lyme disease is caused by a bacterium transmitted to humans
by deer ticks.  Generally deer ticks pick
up the bacterium while in the larval stage from feeding on infected
white-footed mice.  However, certain
other species on which the larvae feed do not harbor the bacterium.  Therefore, if the population of these other
species were increased, the number of ticks acquiring the bacterium―and hence
the number of people contracting Lyme disease—would likely decline.

Which of the following, if true, most strengthens the
argument?

1. Ticks do not suffer any
        adverse consequences from carrying the bacterium that causes Lyme disease
        in humans.
2. There are no known cases of a
        human’s contracting Lyme disease through contact with white-footed mice.
3. A deer tick feeds only once
        while in the larval stage.
4. A single host animal can be
        the source of bacteria for many tick larvae.
5. None of the other species on
        which deer tick larvae feed harbor other bacteria that ticks transmit to
        humans.

  
Answer: