Cambridge B2 First (FCE) — All Questions

The negotiations were completely ___, and no deal was reached. (SUCCESS)

• a.success
• b.unsuccessful✓
• c.succeed
• d.successful

The context 'no deal was reached' needs the negative adjective: prefix 'un-' + 'success' + suffix '-ful' → 'unsuccessful'.

Regular exercise can improve both your fitness and your mental ___. (STRONG)

• a.strengthen
• b.stronger
• c.strongly
• d.strength✓

A noun is needed after 'mental'. 'Strong' becomes the noun 'strength' with an internal spelling change.

She answered every question with remarkable ___. (CONFIDENT)

• a.confidently
• b.confidence✓
• c.confide
• d.confident

After 'remarkable' a noun is required. The adjective 'confident' becomes the noun 'confidence'.

The instructions were written so ___ that nobody could follow them. (CLEAR)

• a.clearness
• b.unclearly✓
• c.clear
• d.clearly

An adverb is needed to describe 'written', and the context (nobody could follow) requires a negative meaning: 'unclearly' (un- + clear + -ly).