In each of the questions given below, four sentences have been given. One out of four sentences may or may not contain an error. Find out which of the following sentence has an error. If all the sentences are error-free then choose ‘ All are correct’ as your answer choice.

Correct Answer: The slowdown in investment didn’t happened because companies were making losses.

Explanation:

Let's analyze the given options to identify the sentence that contains a grammatical error:

1. "Countries have announced their commitment to lofty environmental goals."
This sentence is grammatically correct. The subject "Countries" (plural) agrees with the verb "have announced", and the rest of the sentence follows standard structure and usage.

2. "The foundation stone of the India gate was called the All India War Memorial."
This sentence is grammatically correct. It uses the past tense appropriately to state a historical fact.

3. "Social media platforms regularly manage user content on their website."
This sentence is grammatically correct and meaningful.

4. "The slowdown in investment didn’t happened because companies were making losses."
This sentence contains a grammatical error.
Rule: The auxiliary verb did / didn't (past simple auxiliary) is always followed by the base form of the main verb (infinitive without 'to').
Here, didn't is incorrectly followed by the past tense verb happened instead of the base verb happen.
Corrected Sentence: "The slowdown in investment didn’t happen because companies were making losses."

Therefore, the sentence with an error is: "The slowdown in investment didn’t happened because companies were making losses."