Which of the following is used to avoid bias in a clinical trial?
A. Random assignment
B. High self-confidence
C. Personal preference
D. Financial investment

lunar landing mission. apollo 11 was the first manned mission to land on the moon. the first steps by humans on another planetary body were taken by neil armstrong and buzz aldrin on july 20, 1969. the astronauts also returned to earth the first samples from another planetary body.

explanation:

some of your causes might be acidic rain or natural wildfires that cause the parks to be degraded

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