Answer:
Option D.
Explanation:
Trinomial expression contains 3 terms and the constant term does not vary as variable terms.
Option A.

Expression is a trinomial but without any constant term.
Option B.
x³ + y
It' s a binomial.
Option C.
x
It's a monomial with no constant term.
Option D.
x + 2y + 10
It's a trinomial (having 3 terms) with a constant term 10.
Therefore, Option D is the answer.