The expression obtained by recursively producing a left expression, followed by an operator, followed by recursively producing a right expression is called?

The expression obtained by recursively producing a left expression, followed by an operator, followed by recursively producing a right expression is called?
 
(a) prefix expression
 
(b) infix expression
 
(c) postfix expression
 
(d) paranthesized expression
 
My query is from Trees topic in portion Trees of Data Structures & Algorithms I
 
This question was addressed to me in examination.