In a study of elderly experience of nursing care given at home versus nursing care given in a hospital, the following results are reported: 'Participants preferred medical care at home (M = 56, SE = 1.34) to being cared for in a hospital (M = 48, SE = 1.23). The difference is noted as t(18) = 4.40, p< .05 with an effect size of r = .72.' What does this mean in terms of the significance of the study?

a. Highly significant with a medium sized effect

b. Highly significant with a substantial effect size

c. Not significant with a medium sized effect

d. Not significant but a substantial effect size

(I put a. but it was wrong)