Explanation

(a)(i) The number of pupils who scored between 41 and 50 marks = \(\frac{90}{360} \times 200 = 50\)

(ii) The angles for pupils above 60 marks = 54° + 36° + 18° = 108°

\(\frac{108}{360} \times 200 = 60\)

(b) The fraction of the pupils who scored at least 50 marks : \(\frac{54 + 90}{360} = \frac{2}{5}\)

(c) The modal class = 51 - 60; It has the largest angle in the pie- chart.

Correct Answer: D. government's rejection of a demand for an increase of 50 percent in the cost of living allowances

Correct Answer: A. availability of market and most of the raw materials required

Correct Answer: C. to their best alternatives

Correct Answer: A. 2\(\sqrt{21}\)cm

Explanation

From \(\bigtriangleup\) OMQ find /MQ/ by Pythagoras OQ² = OM² + MQ²

5² = 2² + MQ²

25 = 4 + MQ²

25 - 4 = MQ²

21 - MQ²

MQ² = 21

MQ² = \(\sqrt{21}\)

Length of chord = 2 x \(\sqrt{21}\) = 2\(\sqrt{21}\)cm

Correct Answer: B. wolf

Correct Answer: C. 5

Explanation

(a) Conservation of natural resources is necessary for the following reasons:

(1) The wise use/safe-keeping/ management of natural resources, for the benefit of mankind, (2) To ensure their continuous availability/avoid their decline/extinction.

(b)(i) The following are the methods of soil conservation:

(1) Planting grasses/legumes

(2) Crops must be planted on ridges across slopes

(3) Practicing shifting cultivation/bush fallowing/crop rotation

(4) Avoiding/preventing bush burning

(5) Addition of manure/fertilizer to the top soil

(6) Spreading a layer of vegetable material on cultivated farmland/mulching

(7) Constructing ridges across the slope of the land at intervals/contour ridging

(8) Planting trees/reafforestation

(9) Prevention of over-grazing

(ii) Natural resources that can be conserved are:

(1) Water

(2) Forest

(3) Wildlife

(4) Mineral resources

(5) Genetic mineral/genes

(6) Petroleum/coal/gas/fossil fuel/ iron ore, tin, gold

(c) Factors that negatively affect conservation of forest in West Africa include the following:

(1) Uncontrolled/over-exploitation of forest trees/indiscriminate felling/lumbering of forest trees

(2) Lack of afforestation/tree planting.

(3)Bush burning/wild fires

(4) Non enforcement of conservation laws

(5) Lack of /no knowledge of conservation education/awareness

(6) Use of firewood/charcoal for fuel

(7) Air/soil pollution.

(d) Denitrification stage of the nitrogen cycle: -

• Denitrifying bacteria/certain fungi in the soil
• Convert nitrates into nitrites
• Some bacteria/pseudomonas spp can convert ammonia/nitrite/nitrate into gaseous nitrogen, which is released into the atmosphere, leading to reduction of soil nitrogen content, resulting in reduced soil fertility

Correct Answer: C. 0.879

Explanation

The Spearman's correlation coefficient \(\rho\) is given as:

\(\rho = 1 - \frac{6\sum d^{2}}{n(n^{2} - 1)}\)

= \(\rho = 1 - \frac{6 \times 20}{10(10^{2} - 1)}\)

= \(1 - \frac{120}{990} = \frac{870}{990}\)

= \(0.879\)

Correct Answer: C. iron