`11,` A ( interested in = enjoy )
`12,` C
`13,` D ( ought to = have to )
`14,` B
`15,` A ( isn’t old = young , adj enough to V → too adj to V )
`16,` A
`17,` D
`18,` A
`19,` D
`20,` D
`21,` A ( be able to )
`22,` C
`24,` C
`25,` B
`26,` A ( go on foot = walks to school )