Questions

All atoms of an element have the same number of protons. The number of protons in an element is a primary identifier known as its atomic number. The number of electrons is the same as the number of protons.

Articulation is the proper term for a skeletal joint.

Sun - The Solar Energy is the ultimate source of energy in an ecosystem.

A modem is a hardware device which performs both modulation and demodulation. MODEM means (Modulator-Demodulator).

In the given options, BIS is the odd one from the other three.  NABARD, RBI & IRDA are the bodies related to financial sector of India. The financial sector consists of banks, investment funds, insurance companies and real estate firms. 

BIS stands for Beareau of Indian Standards is a National standard body of India with the activities of standardization, marking and quality certification of goods.