I can’t understand him; he is really a queer fellow.

The correct answer is A. strange.

A queer fellow is someone who is strange or unusual. This could mean that they have unusual habits or interests, or that they behave in a way that is different from most people. It

The other options are not as accurate descriptions of a queer fellow. A careless person is someone who does not take care of things properly. An ordinary person is someone who is not particularly special or unusual. And an unusual person is someone who is different from most people, but not necessarily in a bad way.

In conclusion, the correct answer to the question “I can’t understand him; he is really a queer fellow” is A. strange.