During the query processing the syntax of the query is checked bya.Syntax checkerb.Interpreterc.complierd.Parser

The syntax of the query during query processing is checked by a Parser.

Here's a step-by-step explanation:

1. When a query is submitted, it first goes through a process called parsing.

2. The parser checks the syntax of the query to ensure it follows the rules of the language in which the query is written (like SQL, for example).

3. If the syntax is correct, the query moves on to the next stages of processing which include optimization and execution.

4. If the syntax is not correct, the parser will return an error message, and the query will not be executed.

So, the correct answer is d. Parser.