A notice at a swimming pool reads: 'No one may use the deep end unless he or she has passed the pool's swimming test.' Farhan has passed the pool's swimming test. What follows?

'Unless' sets a bar that must be cleared, not a ticket that must be honoured. Clearing it leaves Farhan eligible, but the pool may also require a minimum age, a lifeguard on duty or a particular hour, none of which the notice rules out. So neither permission nor refusal follows. The fourth option adds a rule about the shallow end that the notice never states.