It should go without saying that the focus of UML is modeling. However, what that means,exactly, can be an open-ended question. (1) is a means to capture ideas, relationships,decisions, and requirements in a well-defined notation that can be applied to many different domains. Modeling not only means different things to different people, but also it can use different pieces of UML depending on what you are trying to convey. In general,a UML model is made up of one or more (2) .A diagram graphically represents things, and the relationships between these things. These (3)can be representations of real-world objects,pure software constructs, or a description of the behavior of some other objects. It is common for an individual thing to show up on multiple diagrams; each diagram represents a particular interest, or view, of the thing being modeled. UML 2.0 divides diagrams into two categories:structural diagrams and behavioral diagrams.(4) are used to capture the physical organization of the things in your system, i.e., how one object relates to another.(5) focus on the behavior of elements in a system. For example, you can use behavioral diagrams to capture requirements, operations, and internal state changes for elements.
空白（4）处应选择（）
A.Activity diagrams
B.Use-case diagrams
C.Structural diagrams
D.Behavioral diagrams
Y(g)+W(g)的进行情况。其中实验I、Ⅱ控温在T1，实验Ⅲ控温在T2，它们的起始浓度均是c(X)=1.0 mol/L，c(Y) =c(W)=0，测得反应物X的浓度随时间的变化如图所示。下列说法不正确的是
缺失，行双端固定桥修复。固定桥试戴时，桥体下黏膜发白，最可能的原因是（）