In an oasis, water is derived from

Step 1: Analyze the question The question asks about the source of water in an oasis, which is a fertile spot in a desert where plants grow and people can settle.

Step 2: Explain the concept An oasis forms where underground water (groundwater) reaches or comes close to the surface. This can happen in three main ways:

• Water from the water table is exposed in a depression or hollow, such as a wind-eroded basin, where the land surface dips down to meet the water table.
• Water rises naturally as a spring or through artesian flow, where pressure forces it up through a fault or crack.
• Water seeps out at the foot of a scarp, or collects from underground rivers.

In each case, the water comes from underground, which supports date palms, crops, and settlements. Examples include the oases of the Sahara, such as Siwa in Egypt and Kufra in Libya.

Step 3: Check the options

• A. Bajada: This is a gently sloping surface at the foot of a mountain, formed from merged alluvial fans in deserts. It is a landform, not a water source.
• B. Underground: Groundwater is the source of oasis water. ✔
• C. Syncline: This is a downward fold of rock layers. Such folds can store water, but a syncline is a structure and not the source itself.
• D. Sill: This is a sheet of igneous rock intruded between rock layers. It has nothing to do with oasis water.

Step 4: Answer The correct option is B. Underground.

Step 5: Exam tip Remember: Oasis = Underground water reaching the surface. If a question asks about the source of an oasis, think "groundwater, spring, or well." Be careful with options like syncline, which sounds related because of artesian basins, but the actual source is still the underground water.