The correct option is D.
The Mexico city was built on the ruins of an old lake. The lake was drained in order to provide the needed land for the city and water has to be regularly pump out of the underground aquifers in order to prevent flooding and also to provide drinking water for the city. This affected the supporting soil structure and result in the sinking of the city. The city has sunk by about 30 feet in the last 100 years and this has caused a lot of damages which are quite expensive to repair.
The correct answer is D. it uses imperfect coordinating structure.
Parallelism refers to the use of the same word form throughout a particular sentence. So, in the example above, in order to achieve parallelism, we would need to change the word 'vacuuming' into 'to vacuum,' in order to keep the consistency with the other two verbs: 'to dust' and '(to) straighten up.'
1. (choice B) 500 ce. continuing
2. (choice D) a book called the history of the kings of Britain , and this
3. (choice C) cited
4. (choice C) many historians believe that the french poet chrétien de troyes was the original writer to introduce lancelot’s character into the romance of arthur and guinevere.
5. (choice B) was enduring
