Interpret the common name

The compound is ethylidene chloride.

In common nomenclature:

• ethylidene refers to the group $\mathrm{CH_3-CH<}$
• chloride here indicates that two chlorine atoms are attached to the same carbon of the ethylidene unit.

So the structure is: $\mathrm{CH_3-CHCl_2}$

Find the parent chain

The longest carbon chain has 2 carbons, so the parent hydrocarbon is: $\mathrm{ethane}$

Locate the substituents

Both chlorine atoms are attached to the same carbon, i.e. carbon 1.

Hence the IUPAC name is: $\mathrm{1,1\text{-}dichloroethane}$

Check the options

• A: 1-Chloroethene $\rightarrow$ incorrect, this is an alkene with one chlorine.
• B: 1-Chloroethyne $\rightarrow$ incorrect, this is an alkyne with one chlorine.
• C: 1,2-Dichloroethane $\rightarrow$ incorrect, chlorines are on different carbons.
• D: 1,1-Dichloroethane $\rightarrow$ correct.

Conclusion

The IUPAC name of ethylidene chloride is: $\boxed{\mathrm{1,1\text{-}Dichloroethane}}$