2. • When something is always true, we use the Simple
Present or the Verb to be.
Examples:
• It is healthy to exercise every day.
• Smoking is bad for you.
• Fishes contain phosphorus.
• Poison kills people.
3. • When something is sometimes true, we use the
modal can.
Examples:
• Working very hard can cause health problems.
• Drinking a lot of alcohol can make you throw up.
• Eating badly can cause heart disease.
4. • When something is a possibility, we use could or
might.
Examples:
• We could go to the gym this weekend.
• Exercise might make you live longer.
• The students coudn’t do the homeworks.
• I might not go to class next Friday.