Answer
c. continuous direct
Explanation
AC means Alternating Current. The current is AC doesn't follow in a specific direction unlike for DC where currect in a conductor follows a specific direction.
Rectification is a processes of converting AC to DC. There are two types of rectification half-wave and full-wave rectification.
Where the currect is not rectified, it appears as a sine curve. When converted it apears as a straight line in a C.R.O. From the choices given the correct answer is c. continuous direct.