Pick out the right option, which expresses the meaning of word 'Invaluable'?

'Invaluable' means extremely useful or important - essentially priceless. The 'in-' prefix here acts as an intensifier (like in 'inflammable'), not a negator. Many students incorrectly think it means 'without value,' but it actually means 'so valuable it cannot be priced.' Priceless is the closest synonym among the options.