Whale / dolphin (big)
Gold / silver (expensive)
Cars / bicycles (fast)
Earth / Moon (big)
Adults / children (old)
Jupiter / Mars (big)
Minute / hour (short)
Planes / cars (fast)
Elephant / cow (heavy)
Amazon River / Thames (long)
Winter / summer (cold)
Arctic / Sahara (cold)
The Sun / the Earth (hot)
Kilometer / meter (long)
Iron / wood (heavy)
Trains / buses (long)
Week / day (long)