Which statement about adjacent angles is correct?

Class 7Lines and AnglesLines and Angles

AAdjacent angles share a common vertex and a common arm but do not overlap.
BAdjacent angles are always equal.
CAdjacent angles always sum to 180°.
DAdjacent angles never share a common side.

Step-by-Step Solution

Adjacent angles have a common vertex and a common arm (side), and their interiors do not overlap. They need not be equal or supplementary.

Answer: A) Adjacent angles share a common vertex and a common arm but do not overlap.

Key idea: Parallel lines and a transversal

When a transversal crosses two **parallel** lines, eight angles form (four at each intersection). They come in special pairs:

- **Corresponding angles**: same position at each intersection (e.g. both top-left). **Equal**.
- **Alternate interior angles**: between the parallel lines, on opposite sides of the transversal. **Equal**.
- **Alternate exterior angles**: outside the parallel lines, on opposite sides of the transversal. **Equal**.
- **Co-interior (same-side interior) angles**: between the parallel lines, on the same side of the transversal. **Supplementary** (sum to 180°).

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