Which sentence is useful for practice because it includes every letter of the alphabet?

The sentence "A quick brown fox jumps over the lazy dog" is considered particularly useful for calligraphy practice because it is a pangram, meaning it contains every letter of the English alphabet at least once. This characteristic makes it ideal for practicing hand lettering, as it allows artists to hone their skills on all 26 letters in a single sentence. By incorporating every letter, calligraphers can focus on the nuances of letterforms, spacing, and overall composition without needing to create multiple sentences.

In contrast, the other options do not include all letters. For instance, "The rain in Spain falls mainly on the plain" mainly repeats certain letters and lacks others, while "She sells seashells by the seashore" focuses on a limited set of letters related to the 's' sound. "How vexingly quick daft zebras jump!" includes most letters but misses some, making it less effective as a comprehensive practice tool. Thus, the correct answer stands out for its complete representation of the alphabet, ensuring a thorough practice experience for calligraphers.