Final answer:
The correct vowel digraph for 'c__ling' is 'oo', resulting in the word 'cooling'. A vowel digraph is a pair of vowels representing one sound.
Step-by-step explanation:
In the given word 'c__ling', the blank spaces require a vowel digraph, which is a pair of vowels representing a single sound. The correct vowel digraph to fill in the blanks is 'oo'. Therefore, the completed word will be 'cooling'. The vowel digraph 'oo' in this word makes a long 'o' sound. Examples of the same sound can also be found in words like 'school' and 'tool'.
Learn more about Vowel Digraph