Of the choices available, 1&2 would fit closest to b), but it strikes me that they are more likely to be unreal presenbts- I don't have the time and I don'
t want to go...
1 & 2 are second conditionals and 3 is a zero conditional:
Yes, we do use the past tense for improbable situations. Most of the time, we don't use the past tense to talk about past time, but the past perfect. However, in colloquial speech, it does get used this way and there are a few cases where we can use the past:
If ever we were late, the teacher would go mad.
(Here, it has a meaning similar to 'every time', so it's 'would' with the meaning of 'used to')