Here we need to exactly measure these lengths.
Also 1m = 100cm
1m 35cm = 135 cm and 1m 20cm = 120cm
Option 1 - cm can measure 30cm = and 1m 20 cm = 120cm
Option 2 – 10cm cannot measure 1m 35cm i.e 135cm
Option – 15cm can measure 30cm, 90cm, 1m 20cm and 1m 35cm
Option 4 – 30cm cannot measure 1m 35cm
Since we want greatest length 15 > 5
Answer = 15cm