6.27A very common 8-bar skeleton

Try:

| C | Am | F | G | | C | Am | Dm G7 | C |

Roman numerals:

| I | vi | IV | V | | I | vi | ii V7 | I |

First four bars:

ends on V.

Open.

Second four:

ends on I.

Closed.

This creates a clear question-answer structure.