对于一窄束射线,在均匀的媒 质中,在无限小的厚度范围内,强度的衰减量正比于入射射线强度和穿透物体的厚 度
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—— How old ________ your brother?—— He's 12.
A. is
B. are
C. was
D. were
—— _______ your phone number?—— It's 6678954.
A. Where's
B. What's
C. How's
D. What
—— _______ they?—— They are Jim's grandparents.
A. What is
B. What are
C. Who are
D. Who is
______ you look like?
A. What do
B. How do
C. What are
D. How are