Certainly! Let's write the correct IUPAC names for each of the given structures step-by-step:
### (a)
The first structure is:
```
Methanal (formaldehyde)
```
### (b)
The second structure can be interpreted as:
```
Propanal
```
### (c)
The third structure is:
```
Propanone (acetone)
```
### (d)
The fourth structure is:
```
Butanone
```
So, the correct IUPAC names are:
- (a) Methanal (formaldehyde)
- (b) Propanal
- (c) Propanone (acetone)
- (d) Butanone