Question 2 can't be b, only A, just look at the textbook
If you look in the Living in Religion book (the orange one from Longman not the blue one), Question 2 would not be b, it would be a. Just look at the table.
If you look at the table it would be more precise to have the 1950's yet, that isn't there, so the difference would of carried upon to the 60's.
60's --> 2 points difference in percentages
70's --> 0.5 points difference in percentages
so question 2 (for multiple choice ) would be A , not b.
(look at my later reply it explains any further doubts from another textbook refernce, i think its on pg 2 now)