$A + B$ 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 $P + R \div Q$,which of the following is true?

$A$ is the father of $C$,and $D$ is the son of $B$. $E$ is the brother of $A$. If $C$ is the sister of $D$,how is $B$ related to $E$?

If $X$ is the brother of the son of $Y$'s son,how is $X$ related to $Y$?

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

$A, B, C, D, E, F$ and $G$ are members of a family consisting of four adults and three children. Two of the children,$F$ and $G$,are girls. $A$ and $D$ are brothers and $A$ is a doctor. $E$ is an engineer married to one of the brothers and has two children. $B$ is married to $D$ and $G$ is their child. $A$ is the son of $C$. Who is $C$?

$A$ party consists of a grandmother,a father,a mother,four sons and their wives,and one son and two daughters for each of the sons. How many females are there in all?