must or should? Why?
Hello!
Could you help me with this?

"If you really must/should smoke, do it outside."

I think to use "should" might be possible here, but the key says that only "must" is correct. Why?

Thank you!

Question

must or should? Why?
Hello!
Could you help me with this?

"If you really must/should smoke, do it outside."

I think to use  "should" might be possible here, but the key says that only "must" is correct. Why?

Thank you!

Answer

Only “must” is correct. Ideally, you would not smoke at all, but if it is truly a necessity, then do it outside.

Answer

Must is a requirement.
Should is more of a suggestion or a preference.
They way your sentence is worded, you must use must.
Here's an example using should.
All smokers should smoke outside. This implies that it is preferred that smoking is done outside.

Answer

should - следует, must - должен. Если тебе действительно это необходимо (если ты действительно должен это сделать из вн.побуждений), сделай это на улице.