题目

The old man fished alone in a small rowboat and he had gone eighty-four days now without taking a fish. In the first forty days a boy had been with him. But after forty days without a fish the boy’s patents had told him that the old man was now bad luck, and ordered the boy to join another boat, which caught three good fish the first week. It made the boy sad to see the old man come in each day with his boat empty and he always went down to help him carry in the fishing lines or take down the old, patched sail. “Santiago,” the boy said to him as they dragged up the boat to the sa已知与的夹角为60°，且||=2，||=1，则与的夹角等于（ ）A．150°B．90°C．60°D．30°