, B, C or D on ANSWER SHEET1. In addition to the established energy sources such as gas ,coal ,oil and nuclear ,there are a num-ber of other sources that we ought to consider. Two of these are hydroelectric and tidal power. These two sources are (21) in that they are both renewable. (22) ,hydropower is more widely used than tidal.ln (23) ,a substantial amount of electricity is already produced in HEP (hydroelectric power)stations worldwide, (24) tidal stations are stillin the very early (25) of development. . As far as geographical (26) is concerned ,HEP projects are to be found on lakes and rivers, whiletidal (27)are constructed only at river mouths where tidal (28) is great .Unfortunately these are (29) in number. At present HEP stations are found mainly in Norway ,Canada ,Sweden and Brazil ,whereas tidal plants are in (30) in France ,Russia and China. As regards capital (31) ,both require very high..investment. On the other hand ,generating(32) are quite low in both cases .ln fact,a large scale HEP plant is capable of producing power more (33) than conventional sources ,such as coal ,oil and nuclear plants. Tidal power also com-pares (34) with nuclear and oil generated electricity, (35) the amount of money on production. (36) HEP stations ,tidalconstructions have alonglife (37).Itis estimated thatthey can operate foroverl00 years. With respect to (38) 0f supply ,tidal stations (39) from HEP ones in that they often can only supply power (40). HEP stations ,however ,provide a constant supply of elec-tricity. 21. [ A] compatible [

] parallel [ C] similar [ D] identical