Many mobile operators already offer a selection of television channels or individual shows, which are sent (1) across their third-generation (3G) networks. In South Korea, television is also sent to mobile phones via satellite and terrestrial broadcast networks, which is far more (2) than sending video across mobile networks; similar broadcasts will begin in Japan in April. Similar mobile-TV networks will also be built in Finland and America, and are being (3) in many other countries.Meanwhile, Apple Computer, which (4) a video-capable version of its iPod portable music player in this October, is (5) a bargain with television networks to expand the (6) of shows that can be purchased (7) viewing on the device. And mobile TV was one of the big (8) at the world’s largest technology fair, the Consumer Electronic Show.(9) all this activity, however, the (10) for mobile TV are unclear. For a start, nobody (11) knows if consumers will pay for it, though surveys suggest they like the idea. One (12) agency of the field, says there will be 125m mobile-TV users by 2010, but many other mobile technologies inspired high hopes and then failed to (13) up to expectations. And (14) people do want TV on the move, there is (15) uncertainty in three areas: technology, business models and the (16) itself.The (17) for mobile TV is vast, in short, but (18) is the degree of uncertainty over how it should actually be put into practice. Most observers do not expect widespread (19) of mobile TV, if it comes at all, until 2008 at the earliest, since building the required ecosystem of technology, partnerships and content will (20) some time. 17（）

A. additive
B. furthermore
C. another
D. further