I need help on this question plzzz

Which statement is a proper biconditional statement for the conditional statement: if a line intersects a line segment at its midpoint, then it is a segment bisector. if a line is a segment bisector, then it intersects the line segment at its midpoint. if a line does not intersect a line segment at its midpoint, then it is not a segment bisector. a line intersects a line segment at its midpoint if, and only if, it is a segment bisector. if a line is not a segment bisector, then it does not intersect the line segment at its midpoint.

What border separates sonora and chihuahua national border state border physical boundary natural boundary

Why slip off slopes are found on the inside of meanders? why river cliffs are found on the outside of meanders?