Eng

Indispensable...

少不了

Indispensable, Inevitable, Inevitably, No doubt

(Can't, Couldn't, Not)

不可或缺

Essential, Indispensable

(Difficult, Forbidden, Hard, No, None, Not allowed)

功不可沒

Indispensable

(Difficult, Forbidden, Hard, No, None, Not allowed)