British investigators conducted a study to examine measles- mumps-rubella (mmr) vaccine history among 1,294 children with pervasive development disorder (e. g., autism and asperger's syndrome) and 4,469 children without such disorders. (they found no association.) this is an example of which type(s) of study?
a. randomize control trial
b. case-control
c. cross-sectional
d. retrospective cohort

B. Case-Control

Explanation:

A case-control is a study that compares a group with an outcome of interest (cases) with a group who do not have the outcome (controls). This study aims to looks back retrospectively to compare how frequently the exposure to a risk factor is present in each group and with that to determine the relationship between that risk factor and the outcome.

So in this case, the cases are children with pervasive development disorder and the control is those without the disorders.

These studies are normally observational because no intervention is attempted.

it has to be understood that the sea water contains a huge amount of sodium and chlorine ions and if they enter the cell of the atlantic cod fish, the cell will shrivel and the fish will die. to avoid such a condition, the fish uses active transport for the purpose of removing the ions against the gradient.

explanation:

the atlantic cod is not a maritime osmoconformer. its native application of salts is less than that of the seawater it lives in. it is continually falling water from the gills to the ocean via osmosis.

countering that, the fish is going to be swallowing seawater. but since its internal collection of salts is lower than seawater, the fish will want to go free of excess salt, and since that's going upon a gradient, then active transport, requiring energy, must be used to pump out the salt. much marine fish use the organs to filter out the salt and these fish discharge very straight urine.