1. I really think you can use either in all cases.
2. a heavy object
3. I think it depends on context. Nromally I'd go for we, though us is widely misused n this case
4. It depends n what you want to say and I don't get it, so I couldn't say
5. I think it should go outside.
1.) Should you use which or that for these 3, please?
(a) The thoughts WHICH or THAT ran through his mind
(b) The knowledge WHICH or THAT he wishes to . . .
(c) He finds a place WHICH or THAT he doesn't recognise
2.) Do you say AN or A heavy object?
3.) Should you say "No - it was not HER or SHE." ?
4.) Would you say "The pointed TOE or TOES of both her shoes." ?
5.) Does the full stop at the end of the sentence, go inside or outside the final bracket (when the words in brackets are at the end of the sentence.)?THANK YOU !
Interesting questions. I apologize in advance for the length of this response, but there are differences between AmE and BrE here.
1. In AmE, there is a strong preference for "that" in restrictive relative clauses (all of these). We usualyy reserve "which" for non-restrictive relative clauses (non-essential information set off by commas). In BrE, both "which" and "that" are equally acceptable for restrictive relative clauses.
BTW, C is correct in the present tense, as you have it. Curmudgeons correction is also correct, but in the past tense.
2. A heavy object. The rule for a/an does not depend on the following letter, but on the following sound. In this case, the "h" is pronounced, so you need "a". If an H word has a silent H, such as hour, use "an".
3. "She" is technically correct, but it is usually only used in formal English. In other uses, "her" is acceptable.
5. Outside brackets or parentheses. When it comes to quotation marks, there is another AmE/BrE difference. In AmE the rule is that terminal periods (final stops) always go inside of the final quotation marks. In BrE, the period can go inside or outside, depending on circumstances. If the period belongs to the quotation, it goes inside the quotation marks; if the period belongs only to the sentence, it goes outside the quotation marks. Even though I am American, I tend to follow the British rule here. It simply makes more sense.