Hi,<br/><br/>Are the sentences below correct?<br/><br/>- He has a good knowledge of chemistry.<br/>- He has good knowledge of chemistry.<br/>- He has a good knowledge. <br/>- He has a knowledge of chemistry.<br/><br/>- He has a good command of German.<br/>- He has good command of German.<br/>- He has a good command.<br/>- He has a command of German.<br/><br/>Thank you,<br/>M