单选题：根据以下资料，回答题。A New Fluoride Optical Fiber American Scientist

根据以下资料，回答题。
A New Fluoride Optical Fiber
American Scientists have developed a new kind of wire that can carry telephone messages for long distances. The new fluoride（氧化物）glass wire, or optical fiber, is a major improvement over the optical fibers now used in many modern communication systems.
Present optical fibers are made from silica glass（石英玻璃）. They are not costly to produce, but the signals carried by these silica optical fibers weaken very quickly. A repeater device（转换器） must be built every 50 kilometers to increase or amplify the signals' strength. Such repeater devices are costly and they need electrical power. This creates special problems for optical fiber systems that cross oceans. Long copper wires are needed to carry electricity from shore to repeater devices under the ocean. Repairing the underwater repeaters is costly and takes much time.
The new fluoride optical fiber is only a little bigger around than a human hair, yet each could carry 10,000 telephone messages at one time for thousands of kilometers. Traditional copper telephone wires can carry only 4 messages. And most importantly, unlike present silica optical fibers, the new fluoride glass wires could carry messages for thousands of kilometers with very few, if any, repeater devices.
The navy scientists developed the new optical fibers for systems that cross oceans, but they said there also would be many other uses for the fluoride glass wires. The new optical wires could be used for long-distance temperature sensing devices. They could be used in some medical operations.
Scientists caution that the new fluoride optical fiber still is only experiment. Researchers have not yet been able to make long tiny wires from fluoride glass.
Which of the following statements is NOT true A．Silica optical fibers are not expensive to produce.
B．Signals carried by silica optical fibers are rather weak.
C．Additional devices are needed for present optical fiber systems.
D．Repeaters bring about special problems for transoceanic communications.