The Biggest cause of Foodborne Illness is
Answer: A
Poor hygiene is the biggest cause of foodborne illness - unwashed hands above all, which transfer bacteria and viruses from a food handler to the food.
The other listed items are ways it happens rather than the underlying cause. Handwashing, temperature control and avoiding cross-contamination prevent most cases.
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A Disease which spreads by contact?
Answer: D
A disease that spreads by contact is contagious.
Every contagious disease is infectious, but not the reverse: malaria is infectious yet not contagious, since it needs a mosquito to carry it. Chickenpox and the common cold spread by contact and are contagious.
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Anything that has Mass and takes up Space-
Answer: B
Anything that has mass and occupies space is matter.
It exists as solid, liquid, gas and plasma. Energy has neither mass in the ordinary sense nor volume, and weight is the force gravity exerts on matter rather than the matter itself.
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Lipids are insoluble in water because lipids are
Answer: A
Lipids are insoluble in water because they are hydrophobic - their long hydrocarbon chains are non-polar.
Water molecules are polar and hold to one another by hydrogen bonds, which the non-polar chains cannot join. Like dissolves like, so lipids dissolve in ether and chloroform instead.
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The first stage in the formation of coal is
Answer: D
Peat still shows recognisable traces of the plants it formed from - leaves, twigs and roots are often visible in it.
It is the first stage of coal formation, with only about 25 to 35 per cent carbon. With increasing pressure and time it becomes lignite, then bituminous coal, then anthracite, and all plant structure is lost.
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Diamond, graphite and fullerene are together called
Answer: A
Diamond, graphite and fullerene are allotropes - different structural forms of the same element in the same physical state.
All three are pure carbon; they differ only in how the atoms are bonded, which is why diamond is the hardest natural substance and graphite one of the softest.
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The two elements that are frequently used for making transistors are
Answer: B
Transistors are made from silicon and germanium.
Both are group 14 semiconductors, whose conductivity can be controlled precisely by doping with traces of boron or phosphorus. Germanium was used in the first transistors; silicon replaced it because it withstands higher temperatures and forms a stable oxide.
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Permanent hardness of water can be removed by adding
Answer: B
Permanent hardness is removed by adding washing soda, sodium carbonate.
It precipitates the calcium and magnesium as insoluble carbonates:
\[ \mathrm{CaSO_4 + Na_2CO_3 \rightarrow CaCO_3 \downarrow + Na_2SO_4} \]
Boiling removes only temporary hardness, which is due to bicarbonates.
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The variety of coal in which the deposit contains recognisable traces of the original plant material is
Answer: D
Peat still shows recognisable traces of the plants it formed from - leaves, twigs and roots are often visible in it.
It is the first stage of coal formation, with only about 25 to 35 per cent carbon. With increasing pressure and time it becomes lignite, then bituminous coal, then anthracite, and all plant structure is lost.
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Diamond is an allotropic form of
Answer: B
Diamond is an allotrope of carbon. Every atom is bonded to four others in a rigid tetrahedral network, which is what makes it the hardest natural substance.
Graphite, charcoal and the fullerenes are the other allotropes; they differ only in how the same atoms are arranged.
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