He stated that (1)/he prefers (2)/ tea than coffee. (3)/ No error (4)

Answer

3

Explanation

It is preposition related error.
Prep.-to is used
withprefer. than is used with other comparative words likerather/better.
Look at the examples given below:
He prefers driving to talking the bus
He prefers during rather than talking the bus.
Hence, to coffee is the right usage.