Name the instrument which can record electrical activity of the brain?
(A) X-ray
(B) ECG
(C) EEG
(D) Ultrasound

Hint: The brain is a very complex organ consisting of millions of nerves, neurons etc., being made up from neurons it transmits messages and signals to perform various activities in the form of electrical signals. Thus, our main objective is to measure and record the signals, to check whether they vary from normal range or not.

Complete Step By Step Answer:
The instrument which can record electrical activity of the brain is called EEG or Electroencephalogram is used to record precisely the electrical activity (signals) of the brain.
In this process we use sensitive metal rods around our head. The brain being made from neurons transmits signals in the form of an electrical pulse. The rods being very sensitive detects the pulse signals and draws the readings.
If our brain has any kind of problems or the brain is damaged the brain functions differently thus the electrical pulses become different.
We measure them and then are able to determine the problem of the brain.
So, the correct option is (C).

Note:
X rays are electromagnetic waves and can pass through our flesh easily but it cannot pass through the bones thus making it effective for us to see the bones. Ultrasound helps to image a person's internals; in this we send sound rays and then receive the reflected rays back to the receiver. Then we draw out the structure of the objects with respect to the reflected rays received. ECG or electrocardiogram is often used alongside other tests to help diagnose and monitor conditions affecting the heart.