The correct answer will stress the differences between the observational study and experimental study - and options a), c) and d) can be true of both.
The correct answer is:
b. Experimental subjects are left free of manipulation
-this is the major difference between the observation and experiment.
Answer: The correct answer is she has a quiet and kind nature.
Explanation: Victor and Teresa are the characters in "seventh Grade" by Gary Soto.
Cotton should be the answer
I think its D.... because it started in China.