Tommy has obsessions about cleanliness and is a compulsive handwasher. Which of the following pieces of evidence would support the view that his obsessive-compulsive disorder is related to operant conditioning? a. Although his parents have punished Tommy many times for handwashing, he continues to engage in the behavior.
b. Tommy sees his brother engage in compulsive handwashing, so he also engages in the behavior.
c. Tommy experiences a large reduction in anxiety whenever he washes his hands, so he continues the behavior whenever he becomes anxious.
d. Tommy read a sign saying that handwashing helps prevent illness.

The Sahara (/səˈhɑːrə/, /səˈhærə/; Arabic: الصحراء الكبرى‎, aṣ-ṣaḥrāʼ al-kubrá, 'the Greatest Desert') is a desert on the African continent. With an area of 9,200,000 square kilometres (3,600,000 sq mi), it is the largest hot desert in the world and the third largest desert overall, smaller only than the deserts of Antarctica and the northern Arctic.[1][2][3]

SaharaThe Greatest Desert

A satellite image of the Sahara by NASA WorldWind

Length4,800 km (3,000 mi)Width1,800 km (1,100 mi)Area9,200,000 km2(3,600,000 sq mi)NamingNative namesa'hraGeographyCountries

List

Algeria

Chad

Egypt

Libya

Mali

Mauritania

Morocco

Niger

Sudan

Tunisia

Coordinates23°N 13°E 

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This video over the Sahara and the Middle East was taken by the crew of Expedition 29 on board the International Space Station.

The name "Sahara" is derived from the Arabic word for "desert" in the feminine irregular form, the singular ṣaḥra'(صحراء /ˈsˤaħra/), plural ṣaḥārā (صَحَارَى /ˈsˤaħaːraː/[4][5][6][7]), ṣaḥār (صَحَار), ṣaḥrāwāt (صَحْارَاوَات), ṣaḥāriy (صَحَارِي).

The desert comprises much of North Africa, excluding the fertile region on the Mediterranean Sea coast, the Atlas Mountains of the Maghreb, and the Nile Valley in Egypt and Sudan. It stretches from the Red Sea in the east and the Mediterranean in the north to the Atlantic Ocean in the west, where the landscape gradually changes from desert to coastal plains. To the south, it is bounded by the Sahel, a belt of semi-arid tropical savanna around the Niger Rivervalley and the Sudan Region of Sub-Saharan Africa. The Sahara can be divided into several regions, including the western Sahara, the central Ahaggar Mountains, the Tibesti Mountains, the Aïr Mountains, the Ténéré desert, and the Libyan Desert.

For several hundred thousand years, the Sahara has alternated between desert and savanna grassland in a 20,000 year cycle[8] caused by the precession of the Earth's axis as it rotates around the Sun, which changes the location of the North African Monsoon. The area is next expected to become green in about 15,000 years (17,000 CE).