To identify the sentence that contains an abstract noun ("nomino ya dhahania"). An abstract noun refers to an idea, quality, or state rather than a physical object or person.

The question asks to identify the sentence that contains an abstract noun ("nomino ya dhahania"). An abstract noun refers to an idea, quality, or state rather than a physical object or person.

• a) "Mvua ilinyesha usiku kucha." (Rain fell all night.)
  • The nouns are "Mvua" (rain) and "usiku" (night). "Mvua" is a concrete noun. "Usiku" refers to a period of time. While time periods can sometimes be considered concrete, the concept of "night" itself is intangible, making it the most plausible abstract noun among the given choices.
• b) "Nilipika chakula." (I cooked food.)
  • The noun is "chakula" (food), which is a concrete noun.
• c) "Watoto walicheza jana." (Children played yesterday.)
  • The noun is "watoto" (children), which is a concrete noun.
• d) "Atakwenda sokoni." (He/She will go to the market.)
  • The noun is "sokoni" (to the market), which refers to a physical place, derived from "soko" (market), a concrete noun.

Comparing the nouns in all options, "chakula," "watoto," and "sokoni" are clearly concrete nouns. "Mvua" is also a concrete noun. However, "usiku" (night), representing a concept of time, is the least tangible and most abstract among the nouns provided.

The final answer is $\boxed{\text{A}}$