[Grammar] These two things are the key/keys to success

[englishteacher79]

Would the correct sentence be:

"These two things are the KEY to success"

OR

"These two things are the KEYS to success"

Or would both be OK and why?

Thanks.

 

[Peedeebee]

Number 2 is the logically correct one because of the plural; things -- keys. But Number 1 would be understood.
Perhaps using the word together in number 1 would make its meaning clear, if that is what is meant.