Step 1: The word oligomenorrhoea is built from oligo, meaning few or scanty, so it points to menses that occur too rarely rather than too heavily or too frequently.
Step 2: A regular menstrual cycle repeats every 21 to 35 days. The diagnostic threshold for calling a cycle infrequent is when the gap stretches past the 35 day mark.
Step 3: Using this rule, any interval greater than 35 days (and up to 6 months) is labelled oligomenorrhoea, which directly matches the option stating cycle more than 35 days.
Step 4: Short cycles below 20 days are the opposite problem (polymenorrhoea), 28 days lies comfortably inside the normal window, and 45 days, while technically infrequent, is not the conventional boundary tested in exams.
\[\boxed{\text{Cycle more than 35 days}}\]