I would like to visit Holland. (A) - The sentence is grammatically correct.

Don't forget to lock the door when you go out. (B) - The sentence is grammatically correct.

If you lose your passport, you will be in trouble. © - The sentence is grammatically correct.

Mary and I weren't writing to each other since we left school. (B) - The correct form of the verb is "haven't been writing" to indicate a continuous action that started in the past and continues up to the present.

I suggest that you give lessons to poor children. (B) - The correct form of the verb is "give" to indicate a suggestion or recommendation.

I learn English so that I can read English books. (D) - The correct conjunction to use is "so that" to indicate the purpose or reason for learning English.

I wish I hadn't made a mistake. (B) - The correct verb form is "hadn't made" to indicate a past regret or wish that something had not happened.

You shouldn't eat quickly. © - The adverb "quickly" should be replaced with the adjective "fast" to modify the noun "food".

I have taught at a primary school for ten years ago. (D) - The phrase "for ten years ago" is incorrect. It should be replaced with "for ten years" or "since ten years ago" to indicate a duration of time.