Zero Conditional

How do we form the zero conditional?
1. If + present ... present / imperative
2. If + past ... would
3. If + present ... will
4. If + past perfect ... would + have + past participle
When do we use the zero conditional?
1. When we speak about conditions which are always true.
2. When we speak about unreal conditions in the present.
3. When we speak about unreal conditions in the past.
4. When we speak about pre-conditions.
Which conditional do we use to refer to scientific facts?
1. zero conditional
2. first conditional
3. second conditional
4. third conditional
Generally speaking, do we use the zero conditional to give instructions?
1. Yes.
2. No.
3. Depending on the type of instruction.
4. Depending on the speaker's opinion.
Which two words may freely be used instead of 'if' in the zero conditional?
1. when / whenever
2. when / unless
3. whenever / unless
4. whenever / after