No25

The question asks to choose the correct form of the word 'лес' to fill in blank 25. The sentence is 'а за дачами начинался (25)....'. The verb 'начинался' (began) governs the nominative or accusative case for the subject, but in this context, it implies 'a forest began'. Considering the options, 'настоящего леса' is in the genitive case, which is incorrect. 'Настоящий лес' is nominative, 'настоящим лесом' is instrumental, and 'настоящему лесу' is dative. The most fitting option for what begins is 'настоящий лес' (nominative case). However, if the sentence implies 'began *with* a real forest', then 'настоящим лесом' (instrumental) could be considered. Given the common phrasing, 'настоящий лес' is the most probable correct answer for the start of something.