Correct option(d) Formed between homologous chromosomes
Explanation :
Polytene chromosomes/salivary gland chromosomes was reported by Balbiani (1881) from cells of salivary glands of Chironomus larva (insect of Diptera group). The polytene chromosomes become giant due to the endoduplication, i.e., repeated replication of chromatids without their separation and cytokinesis. In fact, each polytene chromosome is formed by pairing of two somatic homologous chromosomes which undergo repeated endomitosis to form numerous strands attached to a common large chromocentre.