Isohyets are the lines drawn on a map connecting points having

Answer: (d) Equal rainfall

Isohyets join places of equal rainfall.

The idea

Rainfall maps can join places with the same rainfall total using a line. The total must refer to the same period, such as a month or a year. That line is an isohyet. Equal rainfall does not imply the same temperature, height or pressure.

Why the others are wrong

(a) That is an isotherm.

(b) That is a contour.

(c) That is an isobar.

Also know

Isotherms join equal temperature, contours equal elevation and isobars equal pressure. Isohalines show equal salinity and isobaths equal water depth. An annual isohyet cannot reveal whether rain falls evenly through the year or in one short season. Two places on the same rainfall line can therefore have very different water availability and vegetation.