21.   When hydrogen and oxygen are combined in a fuel cell, an electrochemical reaction generates an electric current.

22.   It seems unlikely that they will jeopardise their superior circumstances by combining in an alliance with Third World workers against capital.

23.   We will now develop these themes and combine them in a systematic way to construct an improved understanding of the relationship between daily life and the nation state.

24.   A compound is a pure substance composed of two or more elements combined in fixed and definite proportions.

25.   Thus carbon and oxygen are invariably combined in a fixed and definite proportion in carbon dioxide.

26.   This states that a pure compound always consists of the same elements combined in the same proportion by weight.

27.   At second level the department offers a series of five half-courses, which students can combine in various ways to make up a full course.

28.   Owen never ceased to marvel at the way in which he combined incredible ingenuity within the rules with total lack of curiosity as to what went on beyond them.

29.   Monetary and fiscal policies could be combined in such a way as to achieve and maintain unemployment rates which differed from the natural rate.

30.   Amazement and fury combined in a sudden rush and she stopped dead in her tracks, whirling round on him.