The correct answer is "18 + 23".

Solution:
To find the correct answer, we find the sum of each expression by rounding (up or down) the addends.

At Option A:
Round the addends to the nearest tens and then add.

43  +  79  =  ?
↓          ↓
40  +  80  =  120

This expression has a sum nearly equal to 120.

At Option B:

25  +  58  =  ?
↓           ↓
30  +  60  =  90

This expression has a sum nearly equal to 90.

At option C:

79  +  29  =  ?
↓          ↓
80  +  30  =  110

This expression has a sum nearly equal to 110.

At the last option D:

18  +  23  =  ?
↓          ↓
20  +  20  =  40

This expression has a sum nearly equal to 40.

So, the desired answer is "18 + 23".