These are the answers I believe to be correct, but please feel free to debate

Also, if you're arguing against an answer, please provide working out and logical reasoning to support your choice. Don't just say "It was A!".
Networks - Question 5: According to Graph Theory, an Eulerian cycle will always exist in an undirected graph where all the vertices have even degree (I was unaware of this). Furthermore (no pun intended), an Eulerian cycle/path can still exist even if the undirected graph is non-planar (as is the case with complete graphs with n number of vertices where n is > 4). This means Question 5 is actually incredibly simple. If you don't however, believe this to be true, allow all the vertices of the pentagon, heptagon and nonagon graphs to be labelled alphabetically in a clockwise direction (i.e. A, B, C, D......).
They would all have at least the following Eulerian cycles (many will exist)
For the complete graph with n vertices where n = 5, an Eulerian cycle will be: A, B, C, D, E, A, C, E, B, D, A.
For the complete graph with n vertices where n = 7, an Eulerian cycle will be: A, B, C, D, E, F, G, A, C, E, G, B, D, F, A, D, G, C, F, B, E, A.
For the complete graph with n vertices where n = 9, an Eulerian cycle will be: A, B, C, D, E, F, G, H, I, A, C, E, G, I, B, D, F, H, A, D, G, A, E, H, B, E, I, C, F, I, D, H, C, G, B, F, A.
Core:
1. E.
2. B.
3. E.
4. D.
5. D.
6. B.
7. D.
8. A.
9. B.
10. D.
11. C.
12. A.
13. E.
Module 1 - Number patterns:
1. D.
2. E.
3. A.
4. D.
5. C.
6. E.
7. D.
8. B.
9. A.
Module 2 - Geometry and trigonometry (courtesy of StumbleBum):
1. C.
2. D.
3. B.
4. B.
5. D.
6. D.
7. C.
8. C.
9. D.
Module 3 - Graphs & relations:
1. B.
2. A.
3. D.
4. A.
5. C.
6. D.
7. A.
8. A.
9. D.
Module 4 - Business mathematics (courtesy of StumbleBum):
1. C.
2. C.
3. E.
4. D.
5. A.
6. C.
7. D.
8. D.
9. A.
Module 5 - Networks & decision mathematics:
1. E.
2. A.
3. C.
4. D.
5. D. (See above for details).
6. A.
7. C.
8. C.
9. D. The explanation for this can be found in this thread:
Can someone explain networks question 9?.
Module 6 - Matrices:
1. D.
2. B.
3. A.
4. E.
5. D.
6. C.
7. B.
8. B.
9. B.