Which features formed natural barriers to expansion and invasion for china

d

explanation:

i think that this is the best answer, but im sorry if this is wrong

immigrants from northern and western europe continued coming as they had for three centuries, but in decreasing numbers

your answer is 1930's

explanation

this is just around the time the great depression was starting and putting the us ecnomy into ecnomic failure causing the goverment to take a much larger rule to try and pieace it back together

2b2t

explanation:

2b2t