Hi,<br/><br/><br/><br/>Which one of the following sentences is more natural to a native ear?<br/><br/><br/><br/>1. I am not <u>sure as to</u> which one of these two is more appropriate.<br/><br/>2. I am not <u>sure</u> which one of these two is more appropriate.<br/><br/>3. I am not <u>sure about</u> which one of the following is more appropriate.<br/><br/><br/><br/>Thanks,<br/><br/><br/><br/>MG