Organisms are classified under the following taxa:
Kingdom
Phylum
Class
Order
Family
Genus
Species
Organisms of the same species can and do interbreed. Organisms in the same genus (the taxa above species) are very similar in their structure and the way they perform life functions, but can't successfully produce offspring. An example is house cats and cougars - they are of the same genus, but of a different species. They look and function similarly, but cannot produce offspring with each other.
Answer:
A. genus, but different species
Tip: The way I remember the order of taxa is by using the mnemonic King Phil Claps Often For Good Science. (: