Answer:
Step-by-step explanation:
From the question given in the picture,
a). Since, NR bisects a straight angle ∠MNP,
   ∠MNR ≅ ∠PNR 
   m∠MNR + m∠PNR = 180°
   2(m∠MNR) = 180°
   m∠MNR = 90° 
   Therefore, ∠MNR and ∠PNR are the right angles.
   Since, QN divides ∠MNR in two parts,
   Therefore, ∠QNR will be an acute angle (less than 90°).
   ∠MNR + ∠SNR = ∠MNS 
   90° + ∠SNR = ∠MNS 
   Therefore, m∠MNS will be more than 90°.
     ∠MNS will be an obtuse angle (greater than 90°).
(b). Since, NR divides ∠MNP and ∠QNS,
     ∠MNR ≅ ∠PNR
      ∠QNR ≅ ∠SNR
      ∠MNQ ≅ ∠PNS
(c). m∠MNR = 90°
      Since, NR bisects ∠QNS, 
      ∠QNR ≅ ∠RNS 
      m∠QNR = m∠RNS = 30° 
      m∠QNR + m∠RNS = 30° + 30°
      m∠QNR + m∠RNS = 60° 
      m∠QNS = 60° [Since, m∠QNS = m∠QNR + m∠RNS]
      m∠QNP = m∠QNS + m∠SNP
      m∠QNP = m∠QNS + (m∠PNR - m∠SNR)
      m∠QNP = 60° + (90° - 30°) = 120°