A diet deficient in calcium can cause osteopenia. The deficiency of calcium may Cause a low bone density which is a condition caused in osteoporosis. Hence the correct answer is B osteopenia.
Answer:
➢ In a mercury thermometer, <u>a glass tube is filled with mercury</u> and a standard temperature scale is marked on the tube. With changes in temperature, the mercury expands and contracts, and the temperature can be read from the scale. Mercury thermometers can be used to determine body, liquid, and vapor temperature.

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Answer:
A = Activator
B = Effector
Explanation:
An activator is a protein which typically binds to a short (50–1500 bp) region of DNA which might be located either upstream (mainly) or downstream of a gene so as to cause increased transcription. This particular region of DNA is known as enhancer and activator is also known as transcription factor. Activator is a trans-acting factor which binds to the cis-acting factor which is enhancer so as to enhance transcriptional expression.
But another protein named as effector may restrict activator from binding to the enhancer leading to a decrease in transcriptional expression by binding to the activator allosterically. Allosteric binding of effector to the activator causes conformational change in activator so it can no longer bind the enhancer.