By default, how many days does CloudTrail store event history in the console?

Maximum 90 days by default. After 90 days, events are no longer visible in the event history.

Which AWS service would you use to analyze CloudTrail logs?

Amazon CloudWatch Logs Insights.

How are CloudTrail logs encrypted when stored in S3 by default?

They are encrypted by default using server-side encryption (SSE). The two main types are ; SSE-S3 & SSE-KMS.

Which service allows you to query CloudTrail logs stored in S3 using SQL-like queries?

Amazon Athena

What is the minimum recommended number of CloudTrail trails in an organization using AWS Organizations for central logging?

The minimum recommended number of trails is one.