The correct option is this: WRITING IS DIFFICULT BECAUSE SO MANY SKILLS ARE INVOLVED.
A topic sentence refers to the sentence which expresses the main idea of the paragraph in which it occurs. The topic sentence is usually the opening sentence in the paragraph; the other sentences in the paragraph just serve to support the topic sentence.
The verbs would be hear and saw.
It all depends on which American Dream you're talking about.
When I Google the American Dream, a website defines it as "...the belief that anyone, regardless of where they were born or what class they were born into, can attain their own version of success in a society where upward mobility is possible for everyone."
This isn't true. It just isn't.
In a perfect world, the dream itself doesn't change, but the rules we have in place to keep specific groups of people lower than others do. I personally believe it can't. I do think it is achievable without hard work; specifically if you aren't a minority, and born into a rich family. But, this is just my personal opinion.
D) the city streets in the summer are bursting with life
