Stocks ended with modest gains Monday after starting off the session in choppy fashion. Leading stocks acted well. The Nasdaq rose 0.4% to its highest close since March 28, 2000. It’s been trading sideways for about a week, pausing after surging 13% off its Oct. 15 low. Helped by the strength in transportation stocks, the S&P 500 climbed 0.3% to another record high. Transports are one sector that’s seeing a large number of new highs.