if air of weight W is filled in a empty ballon of weight W1, the weight of ballon will become W2. suppose the density of air inside and outside the ballon is same , then

​A. w2=w1+w

B w1 = w2-w

C w2 = w1

D W2=W1 -W

W2=W1. Since densities of air inside and outside ballon are identical, weight w of added air inside ballon is equal to weight w of displaced air. Spring balance will not register any difference as ballon will experience uplift force equal to w that exactly cancells weight of added air. Volume of baloon is assumed unchanged, therefore volume of air displaced by baloon itself is unchanged.