a) 5x⁴-8 <----- the tell-tale guy is the exponent of the variable, is 4, so the degree is 4, 5x then minus then 8, two terms, a BInomial
b) 4a²-2a-16 <---- same tell-tale guy, a² has a higher exponent than say "a", so, the degree is the higher exponent, degree of 2
it has 3 terms, thus is a TRInomial
c) 9m³ <---- well, is the only term, variable exponent is 3, so, degree of 3
only one term means is a MONOmial.