Set Theory and Algebra: Which of the following is NOT true?

Question

Let s(w) denote the set of all the letters in w where w is an English word. Let us denote set equality, subset and union relations by =, ⊂ and ⋃ respectively. Which of the following is NOT true?

(a) s(ten) ⊂ s(twenty) 

(b) s(stored) = s(sorted)

(c) s(sixty) ⊂ (s(six) ⋃ s(twenty)

(d) None of these

Answer Given is (d) how?

Comments

{t,e,n}  ⊂ { t,w,e,n,t,y} 
similarly all 3 are true 
so D is the answer.

Answer 1

(a) { t, e, n } ⊂ { t, w, e, n, t, y }   //TRUE

(b) { s, t, o, r, e, d } = { s, o, r, t, e, d }    //TRUE

(c) { s, i, x, t, y } ⊂ { s, i, x, t, w, e, n, t, y }  //TRUE 

All are true..