Prior to the UML, there was no clear leading （） language. Users had to choose from among many similar modeling languages with minor differences in overall （） power. Most of the modeling languages shared a set of commonly accepted concepts that are expressed slightly differently in various languages. This lack of （） discouraged new users from entering the OO market and from doing OO modeling, without greatly expanding the power of modeling. Users longed for the industry to adopt one, or a very few, broadly supported modeling languages suitable for （） usage. Some vendors were discouraged from entering the OO modeling area because of the need to support many similar, but slightly different, modeling languages. In particular, the supply of add-on tools has been depressed because small vendors cannot afford to support many different formats from many different （） modeling tools. It is important to the entire OO industry to encourage broadly based tools and vendors, as well as niche products that cater to the needs of specialized groups.

there was no clear leading （） language

A．programming

B．modeling

C．formal

D．intelligent

阈剂量是指（）

A.临床常用的有效剂量

B.安全用药的最大剂量

C.刚能引起药理效应的剂量

D.引起50%最大效应的剂量

E.引起等效反应的相对剂量