Which of the following reduce the usefulness of ratio analysis when comparing entities that operate in the...

The revenue figure being aggregated from many different activities and sources.

Accounting estimates in respect of depreciation being different between entities.

The effect of a material and unusual item being disclosed separately in the notes.

An entity adopting a policy of revaluing its non current assets.

Ratio calculations being based on historical information.

Ratios being quick and easy to calculate.