Hi! Please help me with this sentence :<br/><br/>His knowing of numbers and alphabet <span style="color:#ff0000;"><b><i>is/are <span style="color:#000000;">(?) </span></i></b><span style="color:#000000;">really good.</span></span><br/><br/><span style="color:#ff0000;"><span style="color:#000000;">Thanks.</span></span><br/><br/><span style="color:#000000;">alchi</span><br/>