The correct answer is their. Because his or her wouldn't make sense because it says they, his also wouldn't make sense for that reason, and the other form of there means for example, "over there"
Answer:
b............................................
It contains exactly 14 lines. i just took the test
1. expert
2. high-tech
3. remote
4. investigate
5. purpose
6. exciting
7. drives
8. knowledge
Hope this helps !! :)