Yes A,B,D are correct because in this we can find three chain isomers, two positions (meso) isomers, two isomers from chiral carbon.

Trichlorocyclobutane is a compound with the molecular formula C4H5Cl3. In this compound, there are three chlorine atoms attached to a cyclobutane ring. Let's analyze each option to determine the correct statements regarding its isomers.

a) It has a total of seven isomers:
To determine the number of isomers, we need to consider different arrangements of the chlorine atoms around the cyclobutane ring. The cyclobutane ring itself is not chiral, so we don't need to consider different orientations of the ring. The possible arrangements of the three chlorine atoms are:
- All three chlorine atoms on the same carbon atom (trichloromethylcyclobutane)
- Two chlorine atoms on one carbon atom and one chlorine atom on the adjacent carbon atom (dichloromethylidene cyclobutane)
- One chlorine atom on each of the four carbon atoms of the cyclobutane ring (tetrachlorocyclobutane)
Overall, there are seven different arrangements of the chlorine atoms, resulting in seven isomers.

b) It has two meso isomers:
A meso compound is a stereoisomer that contains chiral centers but is achiral as a whole due to an internal plane of symmetry. In the case of trichlorocyclobutane, it does not contain any chiral centers, and therefore, it cannot have any meso isomers. Hence, this statement is incorrect.

c) It has two optically active isomers:
To be optically active, a compound must contain chiral centers. Chiral centers are carbon atoms that are bonded to four different groups. Trichlorocyclobutane does not have any chiral centers, as all the carbon atoms in the cyclobutane ring are bonded to three chlorine atoms. Therefore, it does not have any optically active isomers. This statement is incorrect.

d) One isomer is devoid of any chiral carbon:
This statement is correct. As mentioned earlier, trichlorocyclobutane does not have any chiral centers. Therefore, all its isomers are devoid of any chiral carbon.

In conclusion, the correct statements regarding the isomers of trichlorocyclobutane are:
- It has a total of seven isomers.
- One isomer is devoid of any chiral carbon.