这道题选什么啊？？？

根据PMI对hard logic\soft logic\external logical的解释，项目组成员缺少某种技术，一定不属于hard logic\external logical，与soft logic 的意思比较接近，同时，缺少某种技术可以通过多种方式如学习、培训和招聘等方式来解决，因此选项B较贴近。

关于选项A\B\C的具体解释，请参见PMBOK2008英文版 P139-140 或参见下文：
.2 Dependency Determination
Three types of dependencies are used to define the sequence among the activities:
•mandatory dependencies. Mandatory dependencies are those that are contractually required
or inherent in the nature of the work. The project team determines which dependencies are
mandatory during the process of sequencing the activities. Mandatory dependencies often
involve physical limitations, such as on a construction project where it is impossible to erect
the superstructure until after the foundation has been built, or on an electronics project, where
a prototype must be built before it can be tested. Mandatory dependencies are also sometimes
referred to as hard logic.
•Discretionary dependencies. The project team determines which dependencies are
discretionary during the process of sequencing the activities. Discretionary dependencies
are sometimes referred to as preferred logic, preferential logic, or soft logic. Discretionary
dependencies are established based on knowledge of best practices within a particular
application area or some unusual aspect of the project where a specific sequence is desired,
even though there may be other acceptable sequences. Discretionary dependencies should be
fully documented since they can create arbitrary total float values and can limit later scheduling
options. When fast tracking techniques are employed, these discretionary dependencies should
be reviewed and considered for modification or removal.
• External dependencies. The project management team determines which dependencies
are external during the process of sequencing the activities. External dependencies involve a
relationship between project activities and non-project activities. These dependencies are usually
outside the project team’s control. For example, the testing activity in a software project can be
dependent on the delivery of hardware from an external source, or governmental environmental
hearings may need to be held before site preparation can begin on a construction project.