As xenophobia reached new highs right before the start of American inv

Though question as always from egamt.

Lets us delve deeper into this question.

Structure of the sentence

As xenophobia reached new highs right before the start of American involvement in World War I. This clause is a modifier modifying the Immigration Act of 1917 halted immigration from most Asian countries into the United.

Another clause formally the exclusion was ended by the McCarran-Walter Act in 1954.

Error in original sentence.
The way the underlined clause is attached to the remaining sentence raises doubt. Is it absolute phrase. On a casual look it does seem to look like an absolute phrase but upon reading carefully we can see that this is a full Independent clause and it is incorrectly joint to the another independent clause by comma. So we have comma splice error. The two sentences should have been joined by semicolon.

Now let us evaluate each choice.

A incorrect per above reasoning.

B This is interesting we now do not have independent clause rather we have a verb-ing modifier. We now have meaning error and a modifier error. Verb-ing modifier is now modifying previous clause the Immigration Act of 1917 halted immigration from most Asian countries into the United.
The meaning thus derived form this is that the Immigration Act of 1917 halted immigration from most Asian countries into the United led to McCarran-Walter Act in 1954. The meaning here is not good leave B.

C Correct. Absolute phrase is correct we have a noun + noun modifier.

D Meaning here is nonsensical. Per this they halted immigration by having immigration by McCarran-Walter Act in 1954.

E There is no need to use past progressive. Being is wrong. Per this sentence the exclusion was ended over a lengthy period of time by the Act. Not correct. A law is in place the moment it is enacted.