Point out the correct statement.
(a) To avoid parsing ambiguity if the argument is a literal array, you must wrap the literal array in a $lits expression or keep the outer array that designates the argument list
(b) Expressions cannot include field paths and system variables, literals, expression objects, and expression operators
(c) Operator expressions are similar to functions that take arguments
(d) All of the mentioned
I have been asked this question in a national level competition.
My question is based upon Pipeline Optimization topic in portion Aggregation Concepts and Aggregation Mechanics of MongoDB