His - to help was apparent, so none of us asked him to participle in the charity event.

'Alacrity' means brisk and cheerful readiness. However, if none asked him, it implies a *lack* of alacrity? The provided answer 'alacrity' suggests his eagerness was clear, yet maybe they didn't ask? Actually, usually 'reluctance' would fit better if they didn't ask. But 'Alacrity' is the source answer. Maybe his alacrity was *not* apparent? Or his alacrity was so apparent they didn't need to ask? The source key says 'alacrity'.