When you transcribe the word ‘gritty’ or pronounce it /grIti/ , the ‘t’ in the word is heard or visible, so it is not a silent letter.
The answer to this question is ‘A’ asked /a:skt/ or /aeskt/ because it is in a past form and some past forms changes in sound. The (‘-ed) there has the consonant sound ‘-t’ while other words have their ‘t’ in silent forms.

‘Sachet’ /sæjeil/
‘depot’ /depæs/ or /di:pot/ and
‘wrestle’ /’resei/.