Fill in the blanks.
(a) A ________ is an unbroken flat or a low-level land.
(b) The Himalayas and the Alps are examples of _________ types of mountains.
(c) __________ areas are rich in mineral deposits.
(d) The _________ is a line of mountains.
(e) The _________ areas are most productive for farming.
The layer of soil which is not rich in humus but rich in minerals is ___ (Fill in the blank).
Identify the layer of soil which is not rich in humus but rich in minerals. ___ (Fill in the blank).