If you can, do it

The first conditional talks about real or possible future situations: If + present, then will + verb, or an imperative (a command or advice): 'If you feel tired, take a break.'

**The many jobs of could:**

• possibility: 'It could rain today.'
• unreal wish: 'I wish I could fly.'
• past ability: 'As a child I could climb trees.'
• purpose: 'She saved so that she could study.'
• polite request: 'Could you repeat that?'

*Could have* for past possibility or a guess about the past: 'They could have taken the bus.'

Choose the verb form by time:

• general truths: present simple ('It helps students');
• past habits: past ('Students learnt by listening');
• future plans: will ('Schools will include it').