There are several relationships between angles within a transversal of parallel lines.
The complete statement is (b) ∠7 and ∠1 are alternate exterior angles
From the figure (see attachment), we have the following highlights
The above highlights mean that:
Angles 7 and 1 are alternate interior angles
Hence, the text that completes the blank is (b) ∠1
Read more about alternate interior angles at:
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