<span>Their structure, can separate groups of people. This makes it difficult for people, goods, and ideas to move from one place to another. This would also affect the climate.</span>
Answer:
'Had Bought'
Explanation:
The infinitive 'to buy' turns into 'had bought' in past perfect. The PAST TENSE is simply 'bought', but the PAST PERFECT tense is 'had bought'.