Answer:
Option 1.
Explanation:
Like terms : Two terms are called like terms if they have same variables of same degree.
We need to find the expression that can be simplify by combining like terms .
It means we have to find the expression which contains like terms.
In option 1,
The given expression is
In this expression 5cd and -3dc are like terms. On combining like terms we get
So, this expression can simplify by combining like terms.
There are no like terms in other three expressions.
Therefore, the correct option is 1.