Hi<br/><br/>Can you help?<br/><br/>Are these sentences all right?<br/><br/>1. He has an extraordinary concern for the poor.<br/><br/>2. Drug addiction among the teenagers is a matter of great concern.<br/><br/>3. Their whimsical behaviour is a cause of concern. Can we use 'for' in place of 'of'? If yes, what will be the difference in the meaning?