Jim Cramer answered viewers' Twitter from the floor of the New York Stock Exchange, commenting on Qorvo (QRVO), Celgene (CELG), Boston Scientific (BSX), and on why September is a tough month on Wall Street. A viewer asked about Qorvo. Cramer said the company had a disappointing quarter, which brought down other stocks including NXP Semiconductors (NXPI), which he likes better, and Skyworks Solutions (SWKS), which he says to buy in the 70s. Another viewer asked about a good entry point for Celgene (CELG), which Cramer said is a buy at $113 or below. Cramer was asked about his views on Boston Scientific (BSX), which he said is a good company, and that he likes the whole group, including CR Bard (BCR), Medtronic (MDT), Edwards Life Sciences (EW), and St. Jude Medical (STJ). Send your Twitter questions to @JimCramer using #CramerQ.