2) The Mississipppi is longer than the Thames but it isn't as long as the Nile.
3) The Earth is hotter than Mars but it isn't as hot as Mercury.
4) Athens is more polluted than London but it isn't as polluted as Hong Kong.
5) Matt's essay is better than Claire's but it isn't as good as Mirela's.
6) Surfing is more dangerous than running but it isn't as dangerous as skydiving.