The correct sol-fa notation for the passage is

Answer Details

The passage is written in G major (one sharp, F#) with a 2/4 time signature. Reading each bar in tonic sol-fa relative to G as doh:

Bar 1: Two crotchets (quarter notes) on D, which is the fifth degree of G major, giving s : s (soh, soh).

Bar 2: A dotted crotchet on B (the third degree, mi) followed by a quaver on A (the second degree, re). The dot extends the mi by half its value, giving m : -. r.

Bar 3: A dotted quaver on G (doh) followed by a semiquaver on A (re), then a crotchet on F# below the tonic G. Since this F# is the leading note below doh, it is written as t₁ (ti in the lower octave). This gives d . r : t₁.

Bar 4: A minim (half note) on G (doh), filling the entire bar: d : -.

Combining all bars: 2/4 s : s | m : -. r | d . r : t₁ | d : - ||