D. Cd + 2HCl -----> 2CdCl + H2
This correct because single displacement is when you have three elements and one element moves with the other opposite.
Example for you to remember: Single displacement is like going out with your boyfriend and tagging a friend along, then your boyfriend leaves you and tags along with your friend, leaving you all along.
Double Displacement is like having a double date and then switching your dates
Synthesis is like at first you are broken up with your ex and now you have gotten back with him/her
Decomposition is like being with your bf/gf then you end up breaking up
Combustion is really just any type of equation that only uses C, O, and H.
Hopes These Scenarios Help
