Introduction:
The textural classification chart is used in soil mechanics to classify soils based on their particle size distribution. It helps in identifying the engineering properties and behavior of different types of soils. To use the textural classification chart effectively, certain lines must be drawn.

Explanation:
The textural classification chart, also known as the USDA soil textural triangle, is a graphical representation of soil particle size distribution. It consists of three sides which represent three major soil types - sand, silt, and clay. The triangle is divided into different regions that correspond to different soil classifications based on the percentage of sand, silt, and clay present in the soil.

Lines to be drawn:
To use the textural classification chart, lines need to be drawn parallel to the three sides of the triangle. These lines represent the percentages of sand, silt, and clay in the soil sample being classified. The intersection point of these lines on the chart determines the soil classification.

Reason for drawing lines parallel to the three sides:
Drawing lines parallel to the three sides of the triangle ensures that the percentages of sand, silt, and clay are accurately represented. Each side of the triangle represents a specific soil type, and the lines parallel to these sides help in determining the proportion of each soil type in the sample.

Alternate options:
- Option 'B': Drawing lines parallel to only one side of the triangle would not provide a comprehensive representation of the soil sample. It would only consider the percentage of one soil type and neglect the others.
- Option 'C': Drawing lines adjacent to the three sides of the triangle would not accurately represent the percentage of each soil type. Adjacent lines would not account for the proportionality of the soil types.
- Option 'D': Drawing lines adjacent to one side of the triangle would also result in an inaccurate representation of the soil sample. It would not consider the proportionality of the other two soil types.

Conclusion:
To effectively use the textural classification chart, lines must be drawn parallel to the three sides of the triangle. This ensures an accurate representation of the percentages of sand, silt, and clay in the soil sample, leading to the correct soil classification.