【单选题】Read the sections 4.1 to 4.3 of the paper.Which of the following statements from 4.1 presents the central finding of the article?
A.
The coefficient on English language proficiency has the expected sign and is highly statistically significant.
B.
According to the estimates above, the effect on trade of a 20 percent increase in the product of TOEFL scores is roughly equivalent in magnitude to the effect of sharing a native language.
C.
Our results thus demonstrate that improvements in English proficiency, while typically not very large, can nevertheless significantly raise trade.
D.
Our estimates also suggest that improvements in English proficiency have the potential to substantially improve economic welfare