<prompt> True statement about instantaneous mean vector a Equal same as mean QRS vectorb It is drawn through the centre of vector in a direction from base toward apexc Summated vector of generated potential at particular instant caused by inflowing septal depolarizationd When a vector is exactly horizontal and directed toward the persons left side, the vector is said to extend in the direction of 0 degreesabcacdbcdbd  <response>: In a normal heart, the current flows from the base towards apex. So the vector is pointed towards the apex at an angle of 59o. The angle is calculated from a vector running horizontally towards left, which is 0o. Instantaneous mean vector is the summated vector of general potential at a given instant due to septal depolarization. 