What fret would you press on the 4th string to play A?

To play an A note on the 4th string of the guitar, you need to press down on the 2nd fret. The 4th string, which is tuned to D in standard tuning, allows you to reach the A note by moving up two half steps from D. Each fret represents a half step, so moving from the open string (D) to the 2nd fret brings you to E (1st fret), and then to A (2nd fret). Therefore, pressing the 2nd fret on the 4th string accurately produces the A note.