John's rate = 3 chairs per hour on Thursday
Larry's rate = 4 chairs per hour on Friday
For the 2 days, they both work for 7 hours
Let the time taken by John = j and the time taken by Larry = l
Therefore, j + l = 7 hours => This is total time taken for the 2 days
Question: How many chairs did John and Larry assembled last Thursday?
Statement 1: During these two days, John and Larry assembled a total of 25 chairs.
i.e (3 chairs/hour on Thursday) + (4 chairs/hour on Friday) = 25
Work done = rate * time
John's work done = 3 * j => 3j and Larry's work done = 4l
3j + 4l = 25
From question stem j + c = 7 and l = 7 - j
3j + 4 ( 7 - j ) = 25
3j + 28 - 4j = 25
3j - 4j = 25 - 28
y = -3; j = 3
This means that John worked for 3 hours on Thursday
John's workdone = rate * time = 3 * 3 = 9 chairs
John assembled 9 chairs on Thursday, statement 1 is SUFFICIENT

Statement 2 => during these two days, Larry assembled more chairs than John did.
Let chairs assembled by John = x
Let chairs assembled by Larry = y
y > x, apparently, there is nothing to solve here, the only information available in this statement is their work rate and time taken from the question stem and that y > x
Total workdone is unknown, value of x and y is also unknown.
Hence, statement 2 is NOT SUFFICIENT.

Since statement 1 alone is SUFFICIENT, then, answer = OPTION A