Question:
a. The context diagram should depict the system as a single bubble.
b. External entities should be identified clearly at all levels of DFDs
c. Control information should not be represented in a DFD.
d. A data store can be connected either to another data store or to an external entity.
From the statements a, b, c, and d the statements that holds true are

Option A):
a, b and d
Option B):
Only d
Option C):
b and d
Option D):
a and c

Correct Answer is Option D):
a and c