You have greater control over the formatting of the text for a question by clicking on "Rich Content Editor" right above where you would begin typing your text. Once the new editor is open, click on "more..." on the top right. You will then be able to left align the text.
Qualtrics will also accept the formatting of text copied and pasted from Microsoft Word (and probably other programs).

But left align is not block sentence. I thought there is a JS Code.

Apparently, I'm not familiar with block sentence structure. Sorry. You can add JS code to a specific question or item in your survey by clicking on the settings icon under the question number.