Ans. is 'c' i.e., Ordinal scale Statistical scales* There are following type of statistical scales to measure statistical dataFor qualitative data (Categorical Scale)For quantitative data [Metric Scale)i) Nominal scaleii) Ordinal scaleiii) Dichotomous scalei) Interval scaleii) Ratio scaleA. Categorial scale1. Nominal scale# Nominal scale data are divided into qualitative categories or groups, such as male / female, black / white, died / cured, attacked / not attacked, vaccinated / not vaccinate, urban / sub urban / rural.# Example are Race/ethnicity (black/white), marital status (married/unmarried), Religion (Hindu, Muslim/.....), country of birth (India/Nepal/....) ABO blood group, Gender (male/female), disease outcome (cured/died), vaccination status (vaccinated/not vaccinated), Types of anemia (macrocytic/microcytic), and place of living (rural/urban) etc.# There is no implication of order or ratio, means that the data cannot be placed in a meaningful order.2. Ordinal Scale# Here the data can be placed into categories that can be rank ordered (eg. students may be ranked 1st / 2nd / 3rd/4th in their class or into grades A/B/C, the activity of an animal can be rated on a scale of 1 to 6, hardness scale for water etc.)# However, there is no information about the size of the interval ie no conclusion can be drawn about whether the difference between the first and second students is the same as the difference between the second and third.# Example are TNM staging of cancers, Severity of disease (mild, moderate, severe), social class (low, middle, high), classification of person on the base of height (short, medium, tall).3. Dichotomous Scale is a type of nominal scale in which nominal data fall into only two groups eg black/white, died/cured, failed/passed.B. Metric scale1. Interval scale# Interval scale data are like ordinal data in that they can be placed in a meaningful order; in addition, they have meaningful intervals between items, which can be measured.# eg: Temperature on the Celsius scale (the difference between 80deg and 70deg is the same as between 40deg and 30deg)# However, interval scale data do not have an absolute zero, ratios of the scores are not meaningful ie 80deg C of Celsius temperature is not twice as hot as 40degC because 0degC does not indicate a complete absence of heat.2. Ratio Scale# A ratio scale has the same properties as an interval scale, however, because it has an absolute zero, meaningful ratio do exist.# eg. weights, Height, Pulse rate, serum cholesterol, blood glucose, hemoglobin level, time, blood pressure, temperature on the Kelvin scale (not Celsius scale) On the Kelvin scale, zero degrees indicate an absoluteabsence of heat, just as a zero pulse indicates an absolute absence of heartbeat.# Ratio of one value to other is meaningful. For example, pulse rate of 120 beats/minute is twice as fast as a pulse rate of 60 beats per minute, and 300degk is twice as hot as 150degk.* In this question data on anemia are placed into categories that are ordered mild, moderate, sever - ordinal scale should be used.