Looking at the Average Tariff Rate in Australia Since 1930

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

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