Hi! I'm a bit confused about what they call "cleft sentences" and what they call "preparatory it". I think I mix them up, because we always use "lo que" in Spanish. Here are two examples (extracted from BBC Grammar website): 1) PREPARATORY IT (it + be + adj + what clause): It is quite immaterial WHAT you think about it. (Here we use "what" after the adjective) 2) CLEFT SENTENCE: It was a new car THAT my brother bought. (Here we must use "that", never what). But I don't understand if I should use "what" or "that" in sentences like "It's a good thing or It's no surprise / THAT?/WHAT? you've done", because "a good thing" or "no surprise" is not an adjective but a noun. Is that a cleft sentence or an example of preparatory it? Thank you!