Question

[haseli22]

Hi everyone,
Would you please answer to this question:
Which choice best fills the blank?

A: Could you water the trees in the garden?
B: If it ....... so cold, I ....... water them.
1) is not/will 2) is not/would 3) wasn't/will 4) weren't/would

Would you give a reason for the right choice.
Thanks.

[Tdol]

4- because it's cold and I am not going to water them- straight second conditional.