I think you should tell us which you think and why. Or at least which ones you think are the best possible choices. That way people can actually help you instead of just giving you the answers for your test. I'll give you two hints. 1) Temperature can be interpreted to be its own plural (temperatures with an 's'). 2) They all trying to express the exact same thought

You need to match plural and singular. "Temperatures are", or "Temperature is". I'm going to do the correction using plural. 1. The metal must be able to withstand very high temperatureS such as THOSE WHICH are encountered in the pressure compressor. 2. The metal must be able to withstand very high temperatures of the kind which are encountered in the pressure compressor. THIS MAY BE OK, BUT IT'S AWKWARD 3. The metal must be able to withstand very high temperatureS which of the kind are encountered in the pressure compressor. INCORRECT - you can't say "which of a kind" 4. The metal must be able to withstand very high temperatures--something of the kind OF THOSE WHICH are encountered in the pressure compressor. OKAY, KIND OF AWKWARD 5. The metal must be able to withstand very high temperatures which are encountered in the pressure compressor. Question: Which is/are grammatically correct? Do they all have the same meaning? Generally, shorter clauses are less confusing. They mostly mean the same thing, but 5. has more of an implcation that the metal is actually going into the pressure compressor, in my opinion. Oh yes, in case you're wondering how this would work if TEMPERATURE was singular: 1. The metal must be able to withstand very a high temperature such as THAT WHICH IS encountered in the pressure compressor.