WebSQL is a SQL-like (26) language for extracting information from the web. Its capabilities for performing navigation of web (27) make it a useful tool for automating several web-related tasks that require the systematic processing of either ail the links in a (28) , all the pages that can be reached from a given URL through (29) that match a’ pattern, or a combination of both. WebSQL also provides transparent access to index servers that can be queried via the Common (30) Interface.

（27）是（）

A.browsers

B.servers

C.hypertexts

D.clients

（选做，适合选修3-3的同学）

有一台热机，从热源每小时吸收7.2×10⁷J的热量，向冷凝器放出3.6×10⁷J的热量，热机传动部分的热量为从热源吸收的热量的10%，求热机的输出功率和效率．