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

he movement of air through earth's or any planet's atmosphere is called wind, and the main cause of earth's winds is uneven heating by the sun. this uneven heating causes changes of atmospheric pressure, and winds blow from regions with high pressure to those with low pressure.

i hope this : )

d. groundwater flows through the subsoil and deposits minerals.