It is more common to say "With pleasure" or "My pleasure." If you simply say "Pleasure," it does not refer to whose pleasure it is. While that is not technically incorrect, it is a bit awkward.

In addition to what's already been said: in everyday speech, people usually use "Pleasure" as a shortened "It's a pleasure to meet you", for example when shaking hands. It's a casual greeting.

I actually disagree with the answer (by all means). All of the options sound awkward, but "pleasure" sounds the best. To me, "by all means" is closer in meaning to "go ahead" or granting permission. For example, "Can I ask you a question?" "By all means." In the example on your exam, "by all means" doesn't make any sense because the person asked you to do something for them; they did not ask you for permission.

You would normally say 'pleasure' to being thanked. In this case it doesn't make sense to use pleasure unless you say 'it would be my pleasure' which sounds extremely formal. So the correct answer would be 'by all means'.

Jeremy van Dijk Yeah,the question seems quite odd and rude,but it's the original quote from the paper......tipical chinenglish.