It is given that the size of $S_1$ stack is $4$, size of $S_2$ stack is $2$. we can push and pop at any time but for printing the element is only from the stack $S_1$.
Option B):$200,300,400,100$
Here first Pop two items $400,300$ form $S_1$ and push it into $S_2$
$S_1=200,100; S_2=300,400$ from top to bottom. Print $200$ as output.
Pop $300$ from $S_2$ and push it into $S_1$, Print $300$. Now $S_1=100,S_2=400$
Pop $400$ form $S_2$ and push it back into $S_1$. Print 400,100.
In this way, we can generate $200, 300,400,100$ as output.
Option C) $400,200,100,300$
First print $400$ which top most element in $S_1.$
Pop $300$ from $S_1$ and push it into $S_2$.
Now print $200,100$ from $S_1$
Pop $300$ from $S_2$ and push it into $S_1$. print $300$
In this way, we can generate $400,200,100,300$
Option C) $300,200,400,100$
Pop $400$ from $S_1$ and push into $S_2$. Print $300,200$
Pop $400$ from $S_2$ and push it into $S_1$.
So $S_1=400,100$. Now print $400,100$
In this way, we can generate $300,200,400,100$
Option A) can not be generated to print $100$ we have to first pop $400,300,200$ which is not possible because the size of $S_2$ is two.
Option $(B,C,D)$ are correct.