To solve this problem, we need to analyze the given statements:$\newline \bullet$Statement I: Chromosomes become gradually visible under light microscope during leptotene stage.$\newline$ - During the leptotene stage of prophase I in meiosis, chromosomes start to condense and become visible under a light microscope.$\newline$ - This is the first stage of prophase I where the chromatin begins to condense into visible threads.$\newline$ - Hence, Statement I is true.$\newline \bullet$Statement II: The beginning of diplotene stage is recognized by dissolution of synaptonemal complex.$\newline$ - The diplotene stage is characterized by the dissolution of the synaptonemal complex, which is a protein structure that forms between homologous chromosomes during meiosis.$\newline$ - This dissolution marks the beginning of the diplotene stage, where homologous chromosomes start to separate but remain attached at chiasmata.$\newline$ - Hence, Statement II is true.$\newline$Since both statements are true, the correct answer is Option 3: Both Statement I and Statement II are true.