下列关于可转让信用证，说法错误的是（）。 A.可转让信用证只能转让一次 B.可转让

佝偻病、高钙血症、手足抽搐是缺乏矿物质（）。

“弹布尔”是下列（）民族的弹拨乐器？

A.维吾尔族

B.哈尼族

C.鄂伦春族

D.哈尼族

导缆装置的作用是（）。

①导引缆绳由舷内通向舷外，并变换方向；②限制其导出位置及减少磨损；③减少缆绳受力磨损，使其安全。

A.①②

B.②③

C.①③

D.①②③

WLANs are increasingly popular because they enable cost-effective connections among people, applications and data that were not possible, or not cost-effective, in the past. For example, WLAN-based applications can enable fine-grained management of supply and distribution (51) to improve their efficienty and reduce (52) . WLANs can also enable entirely new business processes. To cite but one example, hospitals are using WLAN-enabled point-of-care applications to reduce errors and improve overall (53) care. WLAN management solutions provide a variety of other benefits that can be substantial but difficult to measure. For example, they can protect corporate data by preventing (54) through rogue access points. They help control salary costs, by allowing IT staffs to manage larger networks without adding staff. And they can improve overall network mananement by integrating with customers’ existing systems, such as OpenView and UniCenter. Fortunately, it isn’t necessary to measure these benefits to justify investing in WLAN management solutions, which can quickly pay for themselves simply by minimizing time-consuming (55) and administrative chores.

A. personel B. expenses C. overhead D. hardware

为了放大模拟信号时，不产生明显失真，三极管应该工作在输出特性的线性部分，而且始终工作在输出特性的哪个区域才是正确的（）。

A、截止区

B、放大区

C、饱和区