Due to the law of diminishing marginal utillity, $\mathrm{????},.$

a$.$ the first unit of a product offers more satisfaction than the last unit of the same product

b$.$ the marginal utility curve is upward sloping

c$.$ when marginal utility becomes ncgative, total utility increases

d$.$ there is more satisfaction with each unit of good consumed

e$.$ when marginal utility becomes positive, total utility declines