We are asked to find out which of the given expression is in the simplest form.
Let us analyze each of the given expression
Option 1:
![8m+4n-5mn+7](https://img.qammunity.org/2023/formulas/mathematics/college/7cbj0p2fzbac471ure0gwpg4n461xzoxzd.png)
It seems that this expression is already in its simplest form.
Option 2:
![15bd+5-2b+3d+23](https://img.qammunity.org/2023/formulas/mathematics/college/n1h3ahrek4nlv3zi2wt65z7k7mgyfzvod1.png)
As you can see, the constant terms can be added together.
![\begin{gathered} 15bd-2b+3d+5+23 \\ 15bd-2b+3d+28 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/33ak82whzl13l9it5f8qfv7rb9ocxgog4u.png)
So this expression was not in its simplest form.
Option 3:
![xy+6xy^2-7+12xy](https://img.qammunity.org/2023/formulas/mathematics/college/wwsmkoyo9wdjuwjtelfv42r9sx8y89aa7g.png)
This expression may be further simplified as
![\begin{gathered} xy+6xy^2+12xy-7 \\ x(y+6y^2+12y)-7 \\ x(6y^2+13y)-7 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/k4p9tn2w8flqgfjno4qienuvthx7a78u3z.png)
So this expression was not in its simplest form.
Option 4:
![35-a^2-ab^2+ab-2ab^2](https://img.qammunity.org/2023/formulas/mathematics/college/c5zpjjw3ow56ll8lum2lijuf94e4bdbedv.png)
This expression may be further simplified as
![\begin{gathered} 35-a^2-ab^2+ab-2ab^2 \\ 35-a^2+ab-3ab^2 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/60ijcmfxirnvl23ctf7hfawqrgx5w2mdd7.png)
So this expression was not in its simplest form.
Therefore, now we know for sure that expression 1 was in its simplest form.