Explanation:

- Option 1: "grammar, vocabulary" - This segment is correctly listing the elements of the test.

- Option 2: "This test" - This phrase perfectly introduces what we are discussing.

- Option 3: "and reading comprehension" - The use of "and" here is to conjoin reading comprehension to the other test components correctly.

- Option 4: comprises of - This is where the error lies. "Comprises" should not be followed by "of." The correct phrase should be "comprises grammar, vocabulary, and reading comprehension."

Option 4 is indeed the segment with the grammatical error. .