There’s been a consistent pattern of strong opens and weak closes in the market lately, and it was more of the same Monday as early gains faded, sparked by another drop in oil prices. The Nasdaq and S&P 500 rose 0.8% early, but sellers quickly regained control. The Nasdaq fell 1%, ending just above its 50-day moving average. The S&P 500 wasn’t so lucky. It gave up the key support level, dropping 0.6%.