Choose the right completion.
1. Yesterday I quarreled with my boss about ... I am terribly sorry.
a) who b) which c) that d) whom
2. I decided to quit politics ... I might have a great career in it.
a) because b) though c) since d) whenever
3. I am really anxious about this situation, ..., I hope we can find a solution.
a) ever since b) because of c) although d) however
4 ... various changes during the centuries, the cathedral remained largely unaltered.
a) Despite b) Despite of c) In spite d) Although