1. A group of students help the sick.

2. A group of students helps the sick.

(What is the difference between the two sentence? If both are grammatical, aren the following correct as well? )

3. This is a group of students.
4. These are a group of students.
5. These students are a group of
strong students.
6. Look at the students who are a
group of strong people.

#2 is correct. #1 is incorrect.

The word "group" is the subject and it's singular; therefore, you need the singular form of the verb -- "helps."

#3 is correct.

#4 is incorrect.

#5 is correct; the word "students" (plural) is the subject.

#6 is correct.

The difference between sentences 1 and 2 lies in the subject-verb agreement. In sentence 1, "group" is considered a collective noun, so it is treated as a singular entity, requiring the singular verb form "helps." In sentence 2, "group" is also treated as a collective noun, but it is followed by the plural noun "students," so the plural verb form "help" is used.

Now, let's examine the correctness of the other sentences:

3. This is a group of students.
This sentence is grammatically correct. The singular pronoun "this" is used because it refers to a single entity, which is the group of students.

4. These are a group of students.
This sentence is not grammatically correct. The plural article "these" contradicts the singular noun phrase "a group." Instead, it would be more appropriate to say, "This is a group of students" or "These students are a group."

5. These students are a group of strong students.
This sentence is grammatically correct. The plural article "these" matches the plural noun "students," and "a group of strong students" serves as a description of the students.

6. Look at the students who are a group of strong people.
This sentence is grammatically correct. The plural noun "students" matches the plural pronoun "who," and "a group of strong people" describes the students.