The cutting and gathering of crop after it is matured is called X. After this, grains are separated from the crop by a process called Y. Z is the process of separating the hay and chaff from the grains.Which of the following statements is/are correct regarding X, Y and Z?

• A. Z is done with the help of wind in which grains along with husk is allowed to fall from a height.
• B. X is done mechanically by combine and manually by plough and harrow.
• C. X is the process known as threshing whereas Y is the process known as winnowing.
• D. Both (a) and (b)