There should be a full stop instead of a comma in ‘B’

Actually this one could be correct or incorrect, depending on your stylebook. SOME stylebooks say that if you have AND, the comma is not necessary (which would make your sentence correct.) SOME stylebooks say ALL items in a series need to be followed with commas, even if AND is used next to last. AND SOME stylebooks say that comma is optional.

b. johnson is my attorney , he finally broke the silence .

This is wrong. These are two complete sentences. They need either a period or a semicolon between them. If you use a period, BOTH sentences must begin with a capital letter.

c. giving it their best , none of the swimmers broke johns gores record.

As comma usage goes, this sentence is correct. However, the name should be punctuated thus: John Gore’s

And a purist would add a coordinating conjunction or relative pronoun to your subordinate clause, such as:

Although giving it their best, none of the swimmers broke Johns Gore’s record.

d. patrick , the star player is the only freshman on the team.

This is not correct. “The star player” is an appositive, i.e. restates the subject, and must be set off by TWO commas.

Patrick , the star player, is the only freshman on the team.

Hope this helps.

In D, there will be another comma after the word player.

In B there can be full stop instead of comma and C sounds correct.

You doing your homework?

i had to come back coz i’m not sure if it’s ‘a’ now…lol..sorry