Sentence improvement – correct the verb form after the fixed expression 'look forward to': use a gerund (V+ing) and write 'We look forward to hearing from you.' for formal correspondence clarity and correctness.

Given sentence
'We look forward to hear from you.'

Concept/Approach
In the phrase 'look forward to', the 'to' is a preposition, not the infinitive marker, so it must be followed by a gerund (V+ing): 'to hearing'. This is standard in formal letters.

Step-by-step correction
Replace: 'to hear' → 'to hearing from you'.

Why other options are incorrect
'have heard' → wrong tense/aspect and structure.'listen' → wrong verb meaning and form.'No improvement' → keeps a common but nonstandard error.

Final Answer
hearing