Answer
a. $CH_{3}NH_{3}$ + ion is its conjugate acid.
b. $C_{2}H_{5}NH$+ ion is its conjugate acid.
c. HCl is its conjugate acid.
d. HF is its conjugate acid.
Work Step by Step
a. $CH_{3}NH_{3}$ + ion is its conjugate acid because it can donate a hydrogen proton as it has an extra H+ ion.
b. $C_{2}H_{5}NH$+ ion is its conjugate acid because it can donate a hydrogen proton as it has an extra H+ ion.
c. HCl is its conjugate acid because it can donate a hydrogen proton as it has an extra H+ ion.
d. HF is its conjugate acid because it can donate a hydrogen proton as it has an extra H+ ion.