Which one of the following is not correctly matched?

Answer: (a) Isopleth - A line joining places of equal height

Not correct: an isopleth is any line of equal value; lines of equal height are contours.

The idea

An isoline connects places sharing the same measured value. Its name tells us which variable is held equal. Height has a specific name, contour, while an isopleth is a broader equal-value term in general school usage. The question tests the conventional variable-name pairs rather than the idea of equality itself.

Why the others are wrong

(b) Correct.

(c) Correct.

(d) Correct.

Also know

Isotherm refers to temperature, isobar to pressure and isohyet to rainfall. Isohaline joins equal salinity and isobath equal water depth. Closely spaced contours indicate a steep slope; closely spaced isobars indicate a strong pressure gradient. An isopleth can be used broadly for equal values, so it is less precise than “contour” for elevation.