The correct answers are A. Unique and D. External ID.
The legacy ID should be marked as an External ID because Salesforce can use an external ID field to match records during import, integration, and upsert operations. Salesforce REST API documentation states that records can be inserted or updated using a specified external ID field.
The field should also be marked Unique so that the legacy system ID identifies one Salesforce Account record only. Salesforce documentation explains that an external ID can represent an ID from another external system, and uniqueness helps prevent duplicate matching values.
B is incorrect because encrypted text is not appropriate for a matching/upsert key.
C is incorrect because Required only forces a value; it does not make the field usable for upsert matching or prevent duplicate legacy IDs.

The correct answer is B. Approval Process.
An Approval Process is used when a record must be reviewed and approved before moving forward. Salesforce Trailhead gives a very similar example: opportunities with high discounts requiring approval before proceeding.
Here, Cloud Kicks needs CFO sign-off when a major shoe retail deal has a discount greater than 30% before it can be closed. This is exactly what an approval process is designed to handle.
Why others are incorrect:
Slack message only sends communication.
Email alert only notifies someone.
Field update changes a field value but does not collect formal approval.

The correct answers are A. Tabular format and B. Summary format.
Salesforce reporting snapshots can use custom tabular or summary reports as the source report. Salesforce documentation specifically states that a reporting snapshot source report can be tabular or summary.
Why others are incorrect:
C . Joined format is not supported as a reporting snapshot source report.
D . Matrix format is not supported because matrix reports group by rows and columns, and Salesforce troubleshooting guidance states that matrix reports can't be used with reporting snapshots.

Use a Roll-Up Summary field on Account to count the related Opportunity records. Salesforce roll-up summary fields can calculate values from related records, and the COUNT summary type totals the number of related records. Trailhead also gives the Account and Opportunity example for roll-up summaries.
A formula field cannot count child records by itself. A lookup field only creates a relationship. AppExchange is unnecessary for this standard use case.

The correct answer is C. Approval process.
The key requirement is that the manager's sign-off on free parts must be processed. Salesforce approval processes are designed to automate record approval, define approval steps, assign approvers, and perform actions when records are approved or rejected. Salesforce Trailhead gives a similar discount-management example where discount percentage is tracked and manager approval is requested through an approval process.
Why others are incorrect:
A . High Velocity Sales is for sales engagement/cadences, not approval sign-off.
B . Quotes may help with pricing, but it does not by itself process manager approval.
D . Checkbox can store a value but cannot route approval.