The key answer of exercise 2

a)

1. hopeless, useless
2. nouns → expert, ability, aptitude; adjectives → gifted, skilful, talented hopeless, useless
3. expert → with special skills or knowledge of a subject; gifted → having a natural ability to do something; ability → the state of being able to do something; skilful → good at doing something that you have learnt and practised; aptitude → a natural ability or skill, especially in learning; talented → have a natural ability to do something well; hopeless / useless → very bad at doing something

b)

1. expert, gifted, ability, skilful, aptitude, talented, hopeless, useless
2. Expert, gifted, skilful, hopeless and useless have two syllables. The stress in two-syllable words is usually on the first syllable.