Determine the driving activity for Activity 10001.

Driving Activity Concept:

The driving activity in a backward pass is the one that determines the late start or finish of the dependent activity.

Activity 10001 (Valve House - Complete) is directly dependent on its successor, Activity 11001 (Spillway - Concrete).

Backward Pass Logic:

In backward pass calculations, the late start of Activity 11001 establishes the late finish of Activity 10001 due to their finish-to-start (FS) relationship.

This makes Activity 11001 the driving activity.

Verification:

According to the PSP Study Guide, driving activities are identified based on their logical ties and the critical path's constraints (Ref: PSP Study Guide, Chapter 2A: Activity Relationships and Critical Path Analysis).

Thus, the driving activity for Activity 10001 is A. Activity 11001.