The proposed question and structure has been attached to this answer.
The<em> cis</em>- and <em>trans</em>- isomers are used to denote the alignment of the functional groups to the carbon chain side. From the diagram, we see that:
the two chloro groups on the main compound are in opposite directions (-<em>trans</em>), and not the same sides (-<em>cis</em>)
The bottom extended methyl group is on the 5th carbon as we count from left to right
there's a total of 6 carbon atoms with 1 double bond on the second to third carbon.
Hence the name <u>trans-2,3-dichloro-5-methyl-2-hexene</u>
Explanation: The mantle rock is solid and denser because it is cooler. This means it will sink closer to lower mantle as warmer, lense dense rock/magma moves upwards.