The key answer of exercise 1

ZERO CONDITIONAL

We use it when the result of a condition is certain or inevitable.

CONDITION if + present simple

RESULT present simple

Examples:

• If you heat water to 100 °C, it boils.
• OR Water boils when heated to 100 °C.

FIRST CONDITIONAL

We use it when the result of a condition is likely to happen in the future.

CONDITION if + present simple

RESULT will / won't + base form

Examples:

• If it is sunny today, we will have a picnic in the park.
• OR We will go for a walk if it is sunny today.