I was curios about "карандаша"'s origins... Some further digging didn't let me disappointed.
Карандашей is pencils in the genitive case.
Source: http://www.alphadictionary.com/rusgrammar/genplur.html (#3, stem ends on hush (Ш))
This is absolutely inconsistent and should be fixed. It does not accept "A boy has no pencil" and "A boy does not have a pencil". It insists it must be "The boy does not have a pencil". There is no context enforcing "The" and it must accept negation of a noun (not only negation of a verb) - because it's grammatically correct and it accepts it in other exercises.
каранда́ш (karandáš) [kərɐnˈdaʂ] m inan (genitive карандаша́, nominative plural карандаши́, genitive plural карандаше́й) "pencil" In Russian from the 16–17th centuries. Borrowing from a Turkic language. Compare Turkish karataş (“black slate”), composed of kara (“black”) + taş (“stone”), Tatar кара таш (qara taş, “graphite, black lead”). The origin of epenthetic -н- (-n-) is unclear. Perhaps it was added in colloquial Russian speech to ease the pronunciation. Compare каланча́ (kalančá) for the same epenthesis. Wiktionary