Tổng số hạt cơ bản trong nguyên tử của nguyên tố X là 40. Số khối của hạt nhân nguyên tử
X là
A.22
B.27.
C.26.
D.23.

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
John’s classmates usually make __________ of him because of his poor grades.
A.happiness
B.enjoyment
C.fun
D.entertainment

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
I couldn't sleep because the bed was so __________.
A.uncomfortable
B.inconvenient
C.comfortable
D.convenient

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
One of my friends had to drop out of school because her parents can’t __________ her.
A.provide
B.afford
C.supply
D.support

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
Only two students from each class were __________ to join the competition.
A.selecting
B.opting
C.opted
D.selected

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
My father thinks it is not good for pupils to get __________ in a romantic relationship early.
A.permitted
B.allowed
C.involved
D.helped

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
Everyone has __________ that make them attractive to other people.
A.characters
B.selling points
C.qualities
D.views

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
My grandmother doesn’t understand why boys and girls are __________ to be in the same school nowadays. She went to a single-sex school.
A.put
B.helped
C.allowed
D.called

Tổng số hạt p, e, n trong nguyên tử nguyên tố X là 52. Số khối của hạt nhân nguyên tử X là
A.35.
B.32
C.39.
D.36.

Nguyên tử kali có 19 electron và 20 nơtron, vậy số khối của hạt nhân nguyên tử kali là
A.31.
B.39.
C.34.
D.30.