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C1 Grammar Diagnostic

C1 Grammar Series · Lesson 1 of 3 · Precision Pick

Getting Started

You're about to take a C1 grammar diagnostic designed to test the subtle distinctions that advanced learners need to master.

In each pair, both sentences may look similar — but only ONE is grammatically correct or natural. Your job is to pick the correct one.

Take your time, think carefully, and learn from the explanations. Ready? Let's warm up with two practice pairs.

Practice 1
A
Had she known about the meeting, she would have attended.
✓
B
If she would have known about the meeting, she would have attended.
✗
The Rule
Third conditional: Use "had + past participle" (not "if + would have"). The correct structure is: Had she known → she would have attended. Using "if would have" is non-standard.
Practice 2
A
Not only did he finish the project early, but he also exceeded all expectations.
✓
B
Not only he finished the project early, but he also exceeded all expectations.
✗
The Rule
Inversion after "not only": When "not only" starts a clause, subject-auxiliary inversion is required in formal English. Correct: "Not only did he finish..." Not: "Not only he finished..."
0/10 correct

The Rules Behind It

Here are the 10 grammar rules tested in this diagnostic. Review each one carefully.

Your Results

Once you complete the Precision Pick section, your results will appear here organised by category. Click the lesson links to dive deeper into each grammar topic.