all singular or plural

[envymealways]

<p>this is from a pr sat book </p>

<p>The agenda (features) several contentious issues; (therefore), the council (expects) to see an unusual number of community members, all there to ensure that (his or her voice) will be heard. </p>

<p>the answer is his or her; the only explanation is that "all is plural"
however, i thought whether all is singular/plural depended on the object of the preposition, but there is no preposition following all in this case. please explain. thanks :)</p>

[pokrat]

<p>That underline portion “his or her voice” is obviously referring to community members; therefore, “his or her voice” would have to be changed to “their voices.” Whether or not “all” can be regarded as plural is not important in this case.</p>