Time mgmt questions

You just created the following network logic diagram to describe the planned flow of activities for your project which will start tomorrow:

Which potential inconsistency in the diagram should you solve right now?
 

  Activity E is open ended ( a "dangle") in relation to the finish milestone path convergence.
  Activity F is open ended in relation to the path divergence after the start milestone.
  You cannot calculate a critical path when lags and/or leads are calculated in percent.
  Activities E to F need another task drawn as a hammock to calculate level of effort.

The correct answer is Fiorst choice. Can somebody explain me?

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