I’ll give you a few to choose from:
-There were plenty of jobs (but low-paying) in America
-Gold Rush
-America had an open door policy (at least until the immigration act)
-Social mobility was possible (unlike restrictive social classes in England)
Answer
4 and 5
Explanation
A constant term in an expression is a term that does is independent of any variables. This means that constant term will have non of the variables 
attached to them. In the expression 
we notice that the terms integers 4 and 5 are the only terms that are not coefficients of any of the variables in the expression.
The answer is #2 because it was a steady growth but when 1910 came it started to fluctuate.
I think the answer is no (sorry if i am worng!)
China is growing exponentially as a provider of steel and other products, and it makes complete sense since the nations economy is rising at an incredible pace. The United States traditionally was a huge supplier, but over the past 12 years China has been building structures at an unprecedented rate, and steel being the huge component of large skyscrapers this is one of the biggest reasons for its growth over the decade
