下列症状中最符合十二指肠溃疡合并上消化道出血的是（）

A.呕吐物为咖啡样

B.头晕

C.心悸

D.黄疸

E.寒战

In the following essay, each blank has four choices. Choose the best answer and write down on the answer sheet.

It is more and more usual that users of Information Retrieval (IR) systems must face up to response of hundreds or thousands of (1) documents. A significant proportion of them are moreover (2) or redundant. This is a straight consequence of two well - known facts: the incessant growing of documental databases and the lack of ability of most users to define (3) information needs. In such a framework, further effective retrieval techniques are only part of the solution. Interfaces with alternative ways for organizing and (4) the results returned by a (5) would be of great utility assisting users to find relevant documents. Document clustering may play a central role as an effective technique for organizing query results.

3（）

A．concrete

B．special

C．specific

D．particular