Theory:

The relationships between words can be simple or complicated, as is seen below.

A very common and very important relationship is the pairing between verbs and prepositions, adjectives and prepositions and nouns and prepositions.
For example:
THINK ABOUT, BELIEVE IN, ACCUSE OF, GOOD AT, IN LOVE, SPEAK ABOUT. For a full list of VERB, ADJECTIVE and NOUN PREPOSITION pairs, click on the SEE RELATED DOCUMENTS button below.

Consider the following text:
More and more young people are ...... the advantage of living in ...... country and are deciding to study abroad. They realise it's the best way to learn ..... the customs and the way of life of other people. Student exchanges give teenagers the .... to live somewhere ...... for a school year. ..... they are living abroad, they will eat new food, experience new traditions and learn the way people .... own age live from day to day. Students stay with carefully chosen host families and attend a ..... school. ..... student on the exchange programme has ..... who directly supports them the whole time they are abroad. To qualify as an exchange student, you ..... be aged between 15 and 18 years and be good at a foreign language.

Example:
Sentence 1: More and more young people are ...... the advantage of living in ...... country and are deciding to study abroad.
Explanation:
You RECOGNISE an advantage.
The missing word is RECOGNISING.
Considering the second space,
Explanation:
Living in THIS, THAT or ANOTHER country.
The best choice is ANOTHER country.
The missing word is ANOTHER.

Example:
Sentence 2: They realise it's the best way to learn ..... the customs and the way of life of other people.
Explanation:
The word before the space is the verb LEARN.
It forms a pair with the word ABOUT.
The missing word is ABOUT.

Example:
Sentence 3: Student exchanges give teenagers the .... to live somewhere ...... for a school year.
Explanation:
The possible options for this space are:
THE CHANCE, THE OPPORTUNITY, THE REASON.
The best option is THE OPPORTUNITY.
The missing word is OPPORTUNITY.
Considering the second space,
Explanation:
Possible words that can follow SOMEWHERE are NEW, ELSE, DIFFERENT.
The best option is ELSE
The missing word is ELSE.

Example:
Sentence 4: ..... they are living abroad, they will eat new food, experience new traditions and learn the way people .... own age live from day to day.
Explanation:
The beginning of a sentence in the past continuous of this form would usually start with WHILE.
The missing word is WHILE.
Considering the second space,
Explanation:
The word before OWN could be MY, YOUR, or THEIR.
The best word for this space is THEIR. The missing word is THEIR.

Example:
Sentence 5: To qualify as an exchange student, you ..... be aged between 15 and 18 years and be good at a foreign language.
Explanation:
The word after the space is BE
There are a limited number of words that can be followed by BE.
Possible options are:
TO BE
CAN BE
MUST BE
This sentence would only make sense with MUST
So, the missing word is MUST.