By the beginning of the second trimester of pregnancy, the developing human's
a. organs have not yet begun to form.
b. bones have formed and become rigid.
c. sex can usually be determined.
d. fingers and toes are not yet visible.

C.sex can usually be determined

Explanation:

By the beginning of the second trimester of pregnancy, the developing human's sex can usually be determined. All the essential organs have begun to form, fingers are developed and can form a fist, but the bones throughout the body are still soft and pliable.

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