6. Which biconditional is not a good definition?

A. Two angles are supplementary if and only if the sum of their angles measures 180 degrees.
B. Two angles are vertical angles if and only if they are nonadjacent and are formed by two intersecting lines.
C. Two angles form a linear pair if and only if the angles are adjacent.
D. The sum of two angles is 90 degrees if and only if they are complementary.

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11. Use the Law of Syllogism to determine whether a valid conclusion can be reached from the set of statements/ If a valid conclusion is not possible, choose "not possible."

If you are 18 years old, then you are in college.
If you are in college, then you are not done learning.

A. You are at least 18 years old.
B. If you are 18 years old, then you are not done learning.
C. You are no more than 18 years old.
D. not possible

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12. Write the converse of the following true conditional statement. If the converse is false, write a counterexample.

If you are 18 years old, then you may be eligible to join the U.S. military.

A. if you are eligible to join the U.S. military, then you are 18 years old; true.
B. If you are not 18 years old, then you are not eligible to join the U.S. military; true
C. If you are eligible to join the U.S. military, then you are 18 years old; false.

counterexample: You are eligible to join the U.S. military and you are not 18; you are 19.
D. if you are not 18 years old, then you are not eligible to join the U.S military; false.

counterexample: You are eligible to join the U.S. military and you are not 18; you are 19.