38.X-ray imaging relies on the fact that different biological tissues have distinct attenuation coefficients (µ). An X-ray beam with an initial intensity Io passes through a bone of thickness x and attenuation coefficient u, emerging with intensity 1= Ioe X. If the same X-ray beam instead passes through another tissue of the same thickness but with half the attenuation coefficient (μ'= µ/2), what is the resulting intensity I? (A) I' = 1/2 (B) I'=I (C) I = P/I (D) I= I10 Π (E) I= Vo

6. The basic building blocks of nucleic acids HC are nucleotides. The figure on the right shows a fragment of a nucleic acid structure. Which of the following statements is NOT correct? (A) DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) contain the same nitrogenous bases, but their five-carbon sugars are different. H 0 -O -CH OH (B) A nitrogenous base condenses with a five-carbon sugar to form anucleoside; a nucleoside condenses with phosphoric acid to form a nucleotide; nucleotides undergo condensation polymerization to form a nucleic acid. (C) Under certain conditions, a nucleotide can react with both acids and bases. (D) In nucleic acid molecules, bases undergo complementary pairing through hydrogen bonding. (E) This nucleic acid fragment contains three chiral centers.

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