Looking at the Average Tariff Rate in the United States

Looking at the average tariff rate in the United States since 1930, we see that

A) tariffs have trended downward for most of the period.
B) tariff levels have remained high, at over 50 percent throughout the period.
C) at first tariffs declined, but have recently risen.
D) tariffs were made illegal in the United States in 1955.
E) while we talk about free trade, tariff levels have risen over the last 30 years.