Let the small red toys = x, automatically, small green toys = x
Let the large red toys = y, automatically, large green toys = y
Total number of red toys = x + y, and the total number of green toys = x + y

Target question => what fraction of the total number of green toys is large?
$$i.e\ eveluate\ \frac{y}{x+y}$$

Statement 1: In the production lot, 400 of the small toys are green.
x = 400
But there is no information regarding the value of y. Therefore, statement 1 is NOT SUFFICIENT.

Statement 2: In the production lot, 2/3 of the toys produced are small.
$$1-\frac{2}{3}=\frac{1}{3}$$
1/3 of total toys are large
Large green toys = y / (x+y); large red toys will also be y / (x+y).
$$So,\ all\ large\ toys\ \frac{2y}{2\left(x+y\right)}\ and\ \frac{2y}{2\left(x+y\right)}=\frac{1}{3}$$ $$\frac{y}{x+y}=\frac{1}{3};\ fraction\ of\ large\ green\ toys\ =\ \frac{1}{3}$$
Statement 2 is SUFFICIENT.

Answer = B