Jim Cramer shows off his Apple (AAPL) Watch and answers Twitter (TWTR) questions from the floor of the New York Stock Exchange. On the subject of renewable energy, Cramer says he thinks you have to stay away from the group. He does likes First Solar (FSLR), and says the safest thing to do may be to buy a yield co like the one NRG Energy (NRG) spun off. He also says as oil prices rise, Valero (VLO) is a stock to sell. With Alibaba (BABA) reporting earnings, Cramer says the best way to play it is to buy Yahoo (YHOO). He also thinks the dollar has peaked and that 3M (MMM) is a stock to buy. He does not think Apple has peaked, and that you buy Apple to own it and not trade it.