<u>Answer:</u>
Carbon and silicon both are tetravalent elements as compared to germanium, tin, and lead which are divalent.
That's because Ge, tin, and Pb show inert pair effect and has a greater nuclear effective charge on the 's' electrons due to poor shielding effect. .That's why these elements are not able to share their valence electrons while carbon and silicon does and show "catenation" which is the ability to form long chain molecules.
Carbon is not combustible because when it combines with oxygen its energy increases thus it doesnt combust.
Answer: I would go with B
Explanation: The motor in a circuit isn't moving. That's very vague, but it doesn't show any evidence that an electrical current is going through it, likewise it doesn't show that an electrical current ISN'T going through it. However in regards to this question I would go with B.
Octet means presence of a total of 8 electrons in its valence shell while in case of duplet only 2 electrons are present in valence shell.