The correct option is
B Notice how much sharper the picture appears.
The imperative mood is a verb form which makes a command or a request.An imperative sentence usually does not have a subject, as the order is directed towards the listener, implied by 'you'.
Option A: This sentence tells the listener to notice the sharpness of the picture. Hence it's a command and is in the imperative mood. So, option A is correct.
Option B: This sentence expresses a wish 'I wish...'. It does not express command.
Option C: This sentence is in the indicative mood as it expresses a statement. So, it's not in the imperative mood.
Option D: This sentence is interrogative as it asks something.
These options do not express a command, hence B, C and D are wrong.