Answer:
: reducing agent is CO.
Step-by-step explanation:
a)
![Fe+Cu^(2+)\rightarrow Fe^(2+)+Cu](https://img.qammunity.org/2020/formulas/chemistry/college/e9wi42fx8llof012i2vgx67embt8irn8um.png)
The oxidation state of copper reduces from +2 to 0, it is getting reduced. As
gets reduced, it acts as an oxidising agent.
The oxidation state of iron increases from 0 to +2. Thus, it is getting oxidized. As
gets oxidized, it acts as a reducing agent.
b.
![2Na+Cl_2\rightarrow 2NaCl](https://img.qammunity.org/2020/formulas/chemistry/middle-school/s09lh3g93hwnavzh4rion3g74ddktxbcwo.png)
The oxidation state of chlorine reduces from 0 to -1, it is getting reduced. As
gets reduced, it acts as an oxidising agent.
The oxidation state of sodium increases from 0 to +1. Thus, it is getting oxidized. As
gets oxidized, it acts as a reducing agent.
c.
![C+O_2\rightarrow CO_2](https://img.qammunity.org/2020/formulas/chemistry/middle-school/vo28xxlbb01qg2xafr6gn1s4blg0pujh4t.png)
The oxidation state of oxygen reduces from 0 to -2, it is getting reduced. As
gets reduced, it acts as an oxidising agent.
The oxidation state of carbon increases from 0 to +2. Thus, it is getting oxidized. As
gets oxidized, it acts as a reducing agent.
d.
![NiO+CO\rightarrow Ni+CO_2](https://img.qammunity.org/2020/formulas/chemistry/college/f307cbomm7fw83xocw2aoyc30duz5gfn8u.png)
The oxidation state of nickel reduces from +2 to 0, it is getting reduced. As
gets reduced, it acts as an oxidising agent.
The oxidation state of carbon increases from +2 to +4. Thus, it is getting oxidized. As
gets oxidized, it acts as a reducing agent.