Which is the main cause of the circulation in the upper layer of the ocean? a. Frictional forces called wind stress

b. Temperature conversions

c. Temperature inversions

d. Pycnocline inversions

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a.metals can become magnetic if they have many spinning electrons that create magnetic fields.d.only some metals are attracted by magnets; these metals are called ferromagnetic.

d.wrapping an insulated wire around a metal with ferromagnetic properties and applying an electric current.

t = 1/400 h   ⇔ 0.0025 h ⇔ 9s ⇔ 0.15 m

any of the answers are correct.