The correct answer is: D. Neither I nor II is strong.
Argument I is not strong because it is based on the assumption that the only way to enhance performance of students is to offer education in vernacular medium. However, there is no evidence to support this assumption. In fact, some studies have shown that students who are educated in a foreign language may actually perform better than those who are educated in their native language.
Argument II is not strong because it is based on the assumption that there are no good textbooks available in vernacular medium. However, this is not necessarily the case. There are many good textbooks available in vernacular medium, and the number of these textbooks is increasing all the time.
In conclusion, neither argument I nor argument II is strong.