In order to remove the error of parallax when talking measurements with a metre rule, the eye should be focused
Answer Details
When taking measurements with a meter rule, it is important to avoid parallax error. Parallax error occurs when the eye is not positioned correctly in relation to the meter rule markings, causing an incorrect reading to be taken. To avoid this error, the eye should be positioned directly above the marking being measured, looking vertically downwards at it. This ensures that the eye is perpendicular to the markings and there is no angle between the eye and the markings. Therefore, the correct answer is "vertically downwards on the markings." Focusing the eye slantingly towards the right or left on the markings, or vertically upwards, would introduce an angle between the eye and the markings, resulting in a parallax error.