Final answer:
None of the provided options is a trinomial. A trinomial must consist of three terms, and based on the given choices, there is an expression with two terms, a monomial with one term, and an option that is not applicable.
Step-by-step explanation:
The question is asking which expression among the given options is a trinomial. A trinomial is a type of algebraic expression that consists of three terms, which are typically connected by plus (+) or minus (-) signs. Of the provided options, none is explicitly presented as a trinomial. However, if we consider the provided context with algebraic notations such as dx²-y² and series expansions, it seems like the question might be missing adequate details. Based on the options:
- 1) x y – 13 has two terms and is therefore a binomial.
- 2) 4xyz is a single term and is called a monomial.
- 3) 'Cannot be determined' is not an algebraic expression.
Without further information, we cannot definitively identify a trinomial from the given options. It is possible that the original expressions were not fully provided or there is an error in the question.