I have some questions if you don't mind...

1) ..............., he decided not to swim.

a) The lake is very hot

b) the pond being so cold

c) he has been feeling very ill.

d) since the weather is quite good

e) As he doesn't like going out.

The answer key shows "b" is correct.But I don't understand why. that sentence seems wrong to me.( c can be acceptable to me)

2) If you had taken my advice those days, ................ now.

a) you wouldn't be living in the streets.

b) you could be rich.   

 I know "a" is correct but not "b"?

3) The fact that space exploration has increased since the 1960s  ......................................................

a) is a representative of our small desire to learn more about our solar system.

b) indicates that we are very enthusiastic to learn about our solar system.

The answer is "a" but I think "b" is correct.

4) ..........everyone developing many different skills, specialization came obout as a result of agriculture and this gave rise

    to the beginning of technology.

a) Notwithstanding       b) Even though             c) Nevertheless          d) Although                      e) Instead of 

Which one is correct I couldn't find.

Thanks.