PrepTest 133, Section 1, Question 4

What we’re looking for

Working the answers

• A

  This tells us how to get insect-eating birds to live in the area. That might make birds a practical option, but having another workable option doesn't explain why experts advise against zappers. Both methods could work well. We still need the reason to avoid the zapper.

• B

  Less effective doesn't mean ineffective. Imagine a zapper kills 100 percent of one harmful insect but 90 percent of mosquitoes. The comparison in B would be true, yet the zapper could still be an excellent way to control both.

  Mosquitoes being particularly harmful makes this worth noticing, but B doesn't say how poorly zappers control them or whether birds and sprays do better. It leaves us without a clear reason for the recommendation.

• C

  We're buying a bug killer, not a lamp. A zapper's poor performance as a light source doesn't establish that it's a bad tool for killing insects. Even the electricity comparison is with ordinary lights, not with another way to control insects. More electricity for a different function could be worthwhile.

• D
  Correct

  Which insects are being killed? That's the distinction we were missing. Zappers kill many more beneficial insects and fewer harmful ones than the recommended alternatives. A large number of dead insects can therefore look impressive while being a worse result for pest control.

  Birds and sprays do better on both measures: less harm to helpful insects and more elimination of harmful insects. That gives the experts a concrete reason to recommend them while still accepting that zappers effectively remove flying insects.

• E

  These are developers' claims about certain new sprays, not established safety information about all sprays. More importantly, even a safe spray would show that we have a useful alternative; it wouldn't by itself explain why zappers should be avoided. D supplies the direct disadvantage that E leaves out.