Rewrite the sentence below using the word 'walking'. As they walked on the shore, they could hear the surf. (a) They could hear the surf in walking on the shore. (b) While walking on the shore, they could hear the surf. (c) They could hear the surf walking on the shore. (d) During walking on the shore they could hear the surf.

• A. Only (a) is correct
• B. Only (b) is correct
• C. Only (c) is correct
• D. Only (d) is correct