Answer:
The following sentences have errors: 2, 4,6 & 7
Explanation:
2-He decided that he needed to use part of his Christmas break to start working. // <em>Christmas</em> carries capital letters.
4 He chose to do his project on World War II because he knew that his grandfather was involved in that war, and he could get a lot of information from an interview. // <em>World War II</em> is capitalised.
6 He would first talk about how Germans ....// Nationalities are capitalised.
7 "I'm glad I started this early. This is a lot of work!," he thought to himself. // The second quotation should be placed after the first quotation. There will be two sentences before the clause <em>he thought to himself</em> , and a stop should be put between the two.