Shares of Caterpillar (CAT) - Get Report and Freeport-McMoRan (FCX) - Get Report are on the move Monday, up 2.6% and 13.5%, respectively. So is it time to buy in before it's too late?

These stocks can certainly go higher, but they are most definitely just trades, said TheStreet's Jim Cramer, co-manager of the Action Alerts PLUS portfolio. Cramer spoke from the floor of the New York Stock Exchange as he answered viewers' questions.

So long as oil prices keep going higher, Freeport shares should do okay, he added. Still, he's avoiding these types of "trades" and instead looking for stocks to own for a longer time period.

One such stock isUnder Armour (UA) - Get Report , Cramer said. The company "had a great quarter and I'm a buyer," he said, especially after the stock's massive decline amidst the broader market's recent selloff.

So what about other fitness and apparel plays, like Fitbit (FIT) - Get Report and Skechers(SKX) - Get Report ? Fitbit reports earnings after the close Monday. While Cramer has said he liked the stock in the past, he acknowledged that he has been wrong on it so far. He said investors should see the earnings before making a decision on it.

As for Skechers, Cramer said he wants to see how the company does this quarter before taking a position in it. Shares have been in decline, which tends to indicate that investors aren't very optimistic, he added.

Switching to the payment space, Cramer said he prefers Action Alerts PLUS holdingPayPal(PYPL) - Get Report over First Data (FDC) - Get Report . He also likes Visa (V) - Get Report and MasterCard (MA) - Get Report on a pullback, he said.

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Getting into the health care sector, Cramer said he wants to avoid both Anthem (ANTM) - Get Report and Express Scripts (ESRX) , which are in a "war" with each other.

He then tackled the question on which is better, Celgene (CELG) - Get Report or Biogen (BIIB) - Get Report .

"I really think that Biogen is the better of the two," Cramer said, but added that the entire biotech industry is under pressure from politicians over price gouging. (Biogen is a holding in his Action Alerts PLUS portfolio as well.) If the political jabs continue, Cramer said, it's likely that both stocks are overpriced, given that Biogen just raised the prices for its multiple sclerosis treatment and Celgene acquired Receptos (RCPT) , which could have been at too high a valuation.

Cramer answers viewers' social media questions sent via Facebook(FB) - Get Report and Twitter(TWTR) - Get Report . Contact him @JimCramer on Twitter, and send questions with the hashtag #CramerQ.

At the time of publication, Cramer's Action Alerts PLUS had a long position in BIIB, FB, PYPL and TWTR.