Based on the description of the diagram and the properties of geometric figures, we can analyze each statement to determine which must be true given that line \( DE \) is the perpendicular bisector of segment \( FG \).
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Statement a: \( \angle DHF \) is a right angle.
- This statement is true because a perpendicular bisector creates right angles with the segment it bisects.
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Statement b: \( DE \) is perpendicular to \( FD \).
- This statement is not necessarily true. While \( DE \) is perpendicular to \( FG \), we do not have enough information to conclude that it is also perpendicular to \( FD \).
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Statement c: \( H \) is the midpoint of \( FG \).
- This statement is true because the definition of a perpendicular bisector states that it divides the segment it bisects into two equal parts at the midpoint.
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Statement d: \( DH \cong EH \).
- This statement is true. Since \( DE \) is the perpendicular bisector of \( FG \), the segments \( DH \) and \( EH \) are equal as they are both segments from point \( D \) to point \( H \) and from point \( E \) to point \( H \), respectively.
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Statement e: \( FH \cong GH \).
- This statement is true as well. Because \( H \) is the midpoint of \( FG \) (as established in part c), the segments \( FH \) and \( GH \) are equal.
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Statement f: \( FG \) bisects \( DE \).
- This statement is not true. The segment \( FG \) does not bisect line \( DE \); rather, \( DE \) bisects \( FG \).
Summary of Statements that Must Be True:
- a: True
- c: True
- d: True
- e: True
Thus, the statements that must be true are: a, c, d, e.