ISC2 CC Practice Question: Business Continuity, Disaster Recovery, and Incident Response
A company’s backup strategy: Full backup every Sunday, differential backups Monday through Saturday. On Thursday, the system fails. How many backups are needed to restore the data?
⚠ Common exam trap
Candidates often confuse differential and incremental backup restore requirements; candidates often think all daily backups are needed, but differential only requires the latest one plus the full.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Two: Sunday full and Thursday differential
With a full backup on Sunday and differential backups Monday through Saturday, a restore on Thursday requires the Sunday full backup and the most recent differential (Thursday). Differential backups capture all changes since the last full backup, so only the latest differential is needed along with the full.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Two: Sunday full and Thursday differential
Why this is correct
Restoring requires the Sunday full backup plus Thursday's differential, because differentials capture every change since that full. Wednesday's and earlier differentials are superseded, so only two sets are needed. This satisfies the stem's Thursday failure point, where the latest differential alone completes the chain.
- ✗
One: Thursday differential only
Why it's wrong here
A Thursday differential holds only changes since Sunday's full backup, so restoring it alone leaves the base data absent. It is tempting because the differential is the most recent file, but it would suffice only if the strategy used full backups daily instead of weekly.
- ✗
Four: Monday through Thursday differentials
Why it's wrong here
Differential backups capture everything changed since the last full backup, so Thursday's differential already contains Monday, Tuesday and Wednesday's changes; restoring four differentials is redundant. It is tempting because each day's backup exists, but that pattern describes incremental backups, which would require the full plus each increment.
- ✗
Five: Monday through Thursday differentials plus full
Why it's wrong here
The Sunday full plus Thursday's differential restores everything; adding Monday, Tuesday and Wednesday differentials is redundant because each already includes the prior days' changes. It is tempting because every backup file exists, but that count applies to incremental backups, which capture only changes since the previous backup.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official ISC2 exam blueprint
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