STD 11 - 1. The living world — BIOLOGY STD 11 Science — Question

Assertion $(A)$:

Osteoporosis is characterised by decreased bone mass and increased chances of fractures.

Reason $(R)$ :

Common cause of osteoporosis is increased levels of estrogen.

In the light of the above statements, choose the most appropriate answer from the options given below:

$I$. $ECG$ is of a great clinical significance

$II$. Electrocardiograph is the recording of electrical changes in cardiac muscles during the cardiac cycle

$III$. To obtain a standard $ECG$, a patient is connected to the machine with $3$ electrical electrodes (one to each wrist and to the left ankle)

$IV$. Normal activities of the heart are regulated intrinsically

$V$. Electrocardiogram is the electrical activity of heart

The option with correct statements is