The key answer of exercise 1

FUTURE

PRESENT CONTINUOUS

Fixed plans and arrangements, when we have already decided and we know they will happen.

Example: 

• He's seeing the doctor tomorrow at 5 p.m.
• She's flying to Paris next week.

Signal words

• A time, a date or expressions like: tonight, this afternoon / week / month / summer, tomorrow, tomorrow morning / evening, next month / year, in three days, in three days' time.

PRESENT SIMPLE

Scheduled future events and timetables regarding:

Means of transportation (trains, buses, planes, etc.).

Example: 

• The bus leaves at noon.
• The train arrives at 3 p.m.

Events open to the public (cinema, theater, sport, etc.).

Example: 

The play starts at 7 o'clock.

The concert begins at 8 p.m.

Public institutions or commercial places (school, shops, stores, etc.).

Example: 

• The library opens at 9 a.m. on Mondays.
• The store closes at 10 p.m.

BE GOING TO

Future plans and intentions.

Example: 

• They are going to buy a new house.
• We are going to have dinner at that new restaurant.

Predictions based on present knowledge or evidence.

Example: 

• That vase is on the edge of the table: it's going to fall.
• Look at those dark clouds, it's going to rain soon.

WILL

Future predictions and inevitable future actions or facts.

Example:

• We will be old in 2070.
• There will be a full moon tonight.

Beliefs and predictions about the future (especially with think, be sure, believe, hope, etc.).

Example:

• I think I will receive some presents for my birthday.
• She's sure she will pass the exam.

Offers and promises.

Example: 

• I will wash the dishes for you.
• I promise I will help you with your project.

Spontaneous decisions made at the moment of speaking.

Example: 

• There's no milk! I'll go to the supermarket to buy it.
• It's raining, I'll grab an umbrella.