They wait until they get some news to help them
The sentence in which the underlined infinitive phrase functions as a subject is the last one - to quickly move large groups of people is the purpose of public transportation.
<em>To quickly move </em>is the infinitive phrase, and it is a subject.
While the main idea is usually in the first sentence<span>, the next most common placement is in the last </span>sentence<span> of a paragraph. The author gives supporting information first and then makes the point in the last</span>sentence<span>. Here's a paragraph we can use as an example. Try to locate the topic and the main idea.
</span>
Answer:
The shining treasure of a well-earned diploma offers up riches untold.
