Is it too risky to just learn the biome and leave out soils?
I know at least one biome Q comes up every year but is it possible for them to put up three soil Qs?
its possible for 3 soils to come up but highly unlikely. However the biome could be difficult so knowing a basic brown earth soils essay is a good fallback
Judging from recent years, Human Activity in a Biome is really likely to come up. If you are really pushed for time know your 3/4 biome essays really well and know 1 soil essay really well. An essay on Soil Characteristics or Soil Forming processes is a pretty safe bet. But don't just try learn the essays off by heart, you have to try learn some of the notes that go behind the essays just so you can deal with a tricky question if it comes up.