Find the missing term: 1, 3, 7, 15, 31, ? MCQ with Answer and Explanation

Explanation:
S is Q's father, and P is Q's sister. Hence P is the daughter of S.

Explanation:
From first and second, old =5 or 3. From first and third, books =7 or 3. Common analysis: first and second share 5 and 3, old common. Second and third share 3, but second has and rare old, third books and pens. 'and' common in second and third =3. Then from second, old and rare =3 6 5, and =3 so old/rare =6,5. From first, books are old =7 5 3, and =3 so books/are/old =7,5. Thus old =5, then rare =6.

Explanation:
Each letter is shifted forward by 1: C→D, O→P, D→E, E→F; J→K, A→B, V→W, A→B gives KBWB.