17.Which of these animals is a mollusk?
A. squid B.corals C. spiders D. lobsters
18.All of these are arthropods EXCEPT_______.
A.ant B.clam C.butterfly D.centipede
19.Which force is acting on falling leaves?
A.friction B.gravity C.normal D.tension
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Answer:
17. A.
18. B.
19. B.
Explanation:
17. Mollusca is one of the most diverse groups of animals on the planet, with at least 50,000 living species (and more likely around 200,000). It includes such familiar organisms as snails, octopuses, squid, clams, scallops, oysters, and chitons.
18. Mollusks are soft-bodied invertebrates that exist within hard calcium carbonate shells. There are around 100,000 species in this category, including snails and slugs. The ones we eat, like in the crustacea category, come from the sea: clams, mussels, scallops, oysters and cockles, among others.
19. gravity
The force acting on falling leaf are gravity, air resistance, weight of the leaf, and also normal to the leaf, dragging force may be. Gravity, air resistance, wind, and the buoyant force of the air beneath it.