Concept:
Assumption-based reasoning — identify what is taken for granted in the statement.
Step 1: Analyze the statement.
The statement says that the time required to contain terrorist activities cannot be predicted.
Step 2: Evaluate Assumption A.
"It is impossible to put an end to terrorist activities" → This is a strong/extreme claim.
The statement does not say it is impossible, only that duration is uncertain.
Hence, Assumption A is not implicit.
Step 3: Evaluate Assumption B.
"Efforts to control terrorist activities are on" → This must be true, otherwise the statement about time to contain them would not arise.
Thus, Assumption B is implicit.
Step 4: Final conclusion.
Only Assumption B is implicit.