Cho hình chóp $ S.ABC $ với $ AB=c, BC=a, AC=b $ . Gọi  $K$  là trung điểm của cạnh  $SA$. $M, N$ lần lượt thuộc cạnh $ SC, SB $  sao cho $ \dfrac{SM}{SC}=\dfrac{SN}{SB}=\dfrac{1}{3} $ . Giao tuyến giữa $(KMN)$ và $(ABC) $ là $d$.  $ d\cap AC=E,d\cap AB=F $ . Giá trị  $ EF $ bằng
A.$ a $.
B.$ \dfrac{b}{2} $.
C.$ \dfrac{2b} 3 $.
D.$ \dfrac{c}{3} $.

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
We went to the sale expecting to buy a lot, but we came away ________.
A.empty-handed
B.right-handed
C.left-handed
D.full-handed

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
Jane was invited to stay with a ________ family in Laos.
A.situated
B.local
C.location
D.conditional

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
The college is playing ________ to a group of visiting Russian scientists.
A.guest
B.client
C.host
D.customer

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
Mai ________ for the Singapore Scholarship.
A.paid
B.applied
C.booked
D.registered

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
Was ASEAN ________ on 8 August 1967?
A.committed
B.dominated
C.held
D.formed

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
They soon discovered a ________ interest in music. They both could listen to rock music at any time.
A.mutual
B.dominating
C.sharing
D.popular

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
A country that is governed by a president and politicians elected by the people and where there is no king or queen is called a/an ________ one.
A.socialist
B.domestic
C.conservative
D.republic

Cho hình chóp \[ S.ABCD\] có \[ABCD \] là hình thoi với \[ AC \] \[ =a\sqrt 3 \] , \[ BD=a \] . Gọi E, F lần lượt là trung điểm \[ AD, BC; P \] là trung điểm \[ SE \] . Giao tuyến giữa \[ \left( PCD \right)\] và \[\left( SEF \right) \] cắt $SF $ lần lượt tại $Q$. Tính $PQ? $
A.\[ \dfrac{a}{6} \].
B.\[ \dfrac{a}{3} \].
C.\[ \dfrac{a}{4} \].
D.\[ \dfrac{a}{2} \].

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
________ is the practice of showing respect for God or a god, by saying prayers, singing with others, etc.
A.Hardship
B.Championship
C.Scholarship
D.Worship