PostgreSQL versions up to 9.6 use 3 numbers, for example 9.6.4, and versions 10 use 2 numbers, for example 10.5. The first 2 numbers (up to version 9.6) or the first number (version 10 or later) represent the major version, and the last number represents the minor version.
Looking at recent versions, 9.6 was released in September 2016, version 10 in October 2017, version 11 in October 2018, version 12 in October 2019, and version 13 in September 2020, indicating a pattern of a release once a year in the fall.

Minor updates include bug fixes for each major supported version, with the most recent being 13.1, 12.5, 11.10, 10.15, 9.6.20, and 9.5.24 released simultaneously in November 2020. Prior to that, releases were made every 3 months in August 2020, May 2020, February 2020, November 2019, and August 2019. However, the standard release cycle is  February, May, August, and November each year, with occasional security fix updates.

The support period is typically 5 years from the release of the major version. For example, 9.6, released in September 2016, is scheduled to receive its last minor update in November 2021, when support ends.

So the correct answers are C and D.

For information on when each version is released, when support ends, and more, see:
https://www.postgresql.org/support/versioning/