Institution: বঙ্গবন্ধু শেখ মুজিবুর রহমান বিজ্ঞান ও প্রযুক্তি বিশ্ববিদ্যালয় (BSMRSTU) Exam: A ইউনিট || বঙ্গবন্ধু শেখ মুজিবুর রহমান বিজ্ঞান ও প্রযুক্তি বিশ্ববিদ্যালয় || 2011
Topic: Chemistry (রসায়ন), Subject: General Science (সাধারণ বিজ্ঞান)

Best Answer Explained in Below-:

The question presents two atomic representations: 64 27 C u (Copper with atomic mass 64 and atomic number 27) and 64 30 Z n (Zinc with atomic mass 64 and atomic number 30). To understand their relationship, we need to clarify what "আইসোটোপ", "আইসোমার", "আইসোবার", and "আইসোবেটা" mean.

**আইসোটোপ (Isotope)** refers to different forms of the same element which have the same number of protons (atomic number) but different numbers of neutrons, resulting in different atomic masses. In this case, Copper and Zinc are different elements altogether, so they cannot be isotopes.

**আইসোমার (Isomer)** pertains to molecules with the same molecular formula but different structural arrangements. Since we are dealing with different elements, this term is also irrelevant.

**আইসোবার (Isobar)** refers to atoms that have the same mass number (total number of protons and neutrons) but different atomic numbers. Here, both Copper (Cu) and Zinc (Zn) have the same mass number of 64, but different atomic numbers (27 for Cu and 30 for Zn). This fits the definition of isobars perfectly.

**আইসোবেটা (Isobeta)** is not a standard term in nuclear chemistry and adds no relevant information in this context.

Thus, the correct answer is **C) আইসোবার**, as Copper and Zinc are isobars having the same mass number but differing atomic numbers.