In Yasukawa' s month-long study of blackbirds, the percentage of smaller birds that survived the duration of the study exceeded the percentage of larger birds that survived. However, Yasukawa' s conclusion that size is a determinant of a blackbird' s chances of survival over a month-long period is probably mistaken, since smaller blackbirds are generally younger than larger ones. The statements above, if true, support which one of the following inferences? ['Among the blackbirds that survived the month-long study, there was no relation between size and age.', 'Among blackbirds of the same age, a difference in size may not indicate a difference in chances of survival over a month-long period.', 'With a larger sample of blackbirds, the percentage of smaller birds that survive a one-month period would be the same as the percentage of larger birds that survive.', 'Larger blackbirds of a given age are actually more likely to survive over a one-month period than are smaller blackbirds of the same age.']