Pointing to a lady,a girl said,'She is the daughter-in-law of the grandmother of my father's only son'. How is the lady related to the girl?

$P$ is the brother of $Q$ and $R$. $S$ is $R$'s mother. $T$ is $P$'s father. Which of the following statements cannot be definitely true?

Looking at a portrait of a man,Harsh said,"His mother is the wife of my father's son. Brothers and sisters $I$ have none." At whose portrait was Harsh looking?

$A + B$ means $A$ is the father of $B$; $A - B$ means $A$ is the wife of $B$; $A \times B$ means $A$ is the brother of $B$; $A \div B$ means $A$ is the daughter of $B$.
If $P - R \times Q$,which of the following is true?

If $A + B$ means $A$ is the sister of $B$,$A - B$ means $A$ is the brother of $B$,and $A \times B$ means $A$ is the daughter of $B$,which of the following shows the relation that $E$ is the maternal uncle of $D$?

$E$ is the son of $A$. $D$ is the son of $B$. $E$ is married to $C$. $C$ is the daughter of $B$. How is $D$ related to $E$?