Continuous Variables:
Continuous variables are those that can take on any value within a certain range or interval. They are measured on a continuous scale and can have decimal or fractional values. Examples of continuous variables include age, weight, temperature, and time. In statistics, continuous variables are often represented by real numbers.

Explanation of the Options:
a) Family size: Family size refers to the number of individuals in a family. It can take on any positive integer value, including fractions or decimals. Therefore, family size is an example of a continuous variable.

b) Intelligence: Intelligence is a measure of cognitive abilities that can vary across a wide range. It is typically assessed using standardized tests and is represented by an IQ score. IQ scores can take on any value within a certain range, including decimals. Therefore, intelligence is an example of a continuous variable.

c) Height: Height refers to the vertical measurement of an individual from the ground to the top of their head. It can take on any value within a certain range, including fractions or decimals. Therefore, height is an example of a continuous variable.

d) Attitude: Attitude is a psychological construct that reflects a person's feelings, beliefs, and opinions about a particular topic or situation. Attitudes are typically measured using Likert scales or other rating scales. However, unlike continuous variables, attitudes are not measured on a continuous scale. Instead, they are measured using a limited set of categories or response options (e.g., strongly agree, agree, neutral, disagree, strongly disagree). Therefore, attitude is not an example of a continuous variable.

Conclusion:
In conclusion, all the options provided are examples of continuous variables except for attitude. Attitude is measured using categorical or ordinal scales, which makes it a discrete variable rather than a continuous one.