The two ways of relating what a person has said are 1)direct and 2)indirect (reported speech).In direct speech, the original speaker's exact words are repeated. Direct speech is found in plays and quotations. In indirect/reported speech, the exact meaning is expressed but not necessarily using the original speaker's exact words. Pronouns and possessive adjectives usually change from first or second person to the third person except when the speaker is reporting his own words. Sometimes a noun can be inserted to avoid doubt.
Option D is correct as if is used, shall is changed to should, we to they, to which is used to join the two statements, and positively is used in place of yes, and think is changed to thought.
Options A,B, and C are wrong as if is not used, and, and thinks cannot be used respectively.
The correct answer is D)Sam asked Sue if they should get married to which Sue replied positively and said that she too thought so.