Hong Kong stocks sank in the morning session today, with profit-takers moving in after recent gains, while energy firms again were dragged down by falling oil prices. The Hang Seng Index dropped 0.65 percent to 22,848.38 points. The benchmark Shanghai Composite Index was flat, edging down 0.83 points to 3,088.88 points, while the Shenzhen Composite Index, which tracks stocks on China’s second exchange, gained 0.40 percent to 2,032.19 points.