What type of circulatory system do mollusks have? Which animal in this phylum is the
exception?

Molluscs with the exception of cephalopods have an open circulatory system I.e.the blood circulates with in vessels from the heart but it also fills open lacunas or cavities. In annelids the cieculatory system is closed, i.e. the blood circulates only inside blood vessels.

the correct answer is - d. china has a large and growing population.

the fact that china has a large (the biggest) population, and it is still growing, doesn't hinder the agriculture production in the country. in fact, it can for increased production in the agriculture, since there's more labor force, as well the sheer mass of people produces lots of scientists that come up with new inventions as to how to improve this sector. nice example is the inner mongolia region in china, in general dominated by the gobi desert, but few scientist came up with a nice idea as to how to make the region productive by using plants that are very resistant to droughts, so lots of people have been employed, and the region is becoming greener and greener each year, and the production of food in this region is also increasing.