6. Aorven brought enough money to buy 30 balloons to the store. Upon arriving, he found that the balloons were on sale: if the first balloon is bought at the original price, then the second balloon can be bought at a $\frac{1}{3}$ discount off the original price. How many balloons can Aorven buy at most?
(A) 33
(B) 34
(C) 36
(D) 38
(E) 39
6. C.

Assume the original price of a balloon is $x$ dollars. Alvin spends $x+\left(1-\frac{1}{3}\right) x=\frac{5}{3} x$ dollars on two balloons. Therefore, he can buy at most $2 \times \frac{30 x}{\frac{5}{3} x}=36$ balloons.