Explanation:
> "Must you always ____ lies? Why don't you ____ the truth for once?"

We are looking for the correct verbs to fill in the gaps. The first part involves lying, and the second part asks about telling the truth.

Now, let's analyze the options:

- A. speak — "Speak" is generally used for verbal communication, but not specifically for lies or truth. It wouldn't work as well here. Incorrect.
- B. say — "Say" is used when you're quoting or stating something, but it’s less common in the context of telling lies. Incorrect.
- C. talk — "Talk" generally refers to conversational speech, but it doesn’t fit the context of telling lies or truth. Incorrect.
- D. tell — "Tell" is the most appropriate verb when referring to both lies and truth, as it’s used in contexts like "tell lies" or "tell the truth." Correct.
- E. utter — "Utter" refers to speaking, but it’s usually more formal and doesn’t fit naturally with "lies" and "truth." Incorrect.