11.  A bullet exceeding the speed of sound creates two shock waves.

12.  A business rate will also be levied, but both these two components of local authority finance will be radically restructured.

13.  A cable system has two types of customers-advertisers and consumers who subscribe to a package of programming offered by the cable operator.

14.  A cemetery and a museum are two different institutions that have different functions.

15.  A central issue is whether two independent executives can share power effectively.

16.  A clothes-line hangs between two high windows, hovering above like a tawdry hammock from the sky.

17.  A colour photocopier was installed, in addition to the two black and white copiers.

18.  A combination of the two processes means that you can use seven years of unused tax relief in one tax year.

19.  A comparison of the two figures shows the estimated profit on investment.

20.  A concise way of illustrating it is to consider two questions.