Let John's chair per working hour = j
Let Larry chair per working hour = l
$$j+l=7$$
Statement 1=> During these two days, John and Larry assembled a total of 25 chairs
$$3j+4l=25\ \ \ \ \left(from\ workdone=rate\cdot time\right)$$
$$j+l=7$$
$$l=7-j$$
Substitute the value of 'l' into the above expression,
$$3j+4\left(7-j\right)=25$$
$$3j+28-4j=25$$
$$-j=-3$$
$$j=3$$
So, John assemble 3*3=9 chairs. Hence, statement 1 is SUFFICIENT

Statement 2=> During these two days, Larry assembled more chairs than John did. This statement does not provide us with the total number of chairs they assembled. Therefore, statement 2 is NOT SUFFICIENT.

Since statement 1 alone is SUFFICIENT; then we have the correct answer to be option A.

Thanks