Given that USA accounts for 20 percent of the total production of soyabean in the world then what percentage of the total food crops production of the world is accounted by USA?

Given: 20% of the world's total soyabean production is from the USA

Thus, we can consider the world's total production (160 million tonnes) as P.

Thus, the USA's production of soyabean = 0.2 x 0.35 x P = 0.07P = 7% of the total production of crops. 

Soybean production constitutes 25% of the total crop production in the USA.

Thus, percentage of total crop production accounted by the USA = $$\frac{7\%}{0.25}=28\%$$

Hence, the answer is option C.