A. $\widehat {mOy}$

B. $\widehat {yOn}$

C. $\widehat {xOn}$

D. $\widehat {xOy}$

A. $\widehat {NMI}$

B. $\widehat {MNI}$

C. $\widehat {NIP}$

D. $\widehat {IPN}$

A. ${45^o}$

B. ${135^o}$

C. ${90^o}$

D. ${180^o}$

A. $\widehat {xOt} > \widehat {tOy}$

B. $\widehat {xOt} = \widehat {tOy} = 2\widehat {xOy}$

C. $\widehat {xOt} = \frac{1}{2}\widehat {tOy}$

D. $\widehat {xOt} = \widehat {tOy} = \frac{1}{2}\widehat {xOy}$.