A - This compares the rate to the 1970's. Also, a rate cannot be considered fast.
B - See A above.
C - Correct.
D - See A above.
E - "Greater" is not the right word to use here.
It might be worthwhile to point out that the term "1970's" is not possessive.
I tend to disagree : "rate of" (= speed/frequency) can be considered fast. For example: X's rate of travel was faster than that of Y
I will choose C over B, because it is more concise.