A.một bước sóng.
B.một phần tư bước sóng.
C.hai lần bước sóng.
D.một nửa bước sóng.

A.là phương ngang.
B.là phương thẳng đứng.
C.trùng với phương truyền sóng.
D.vuông góc với phương truyền sóng.

A.\(_6^{14}N\)
B.\(_6^8C\)
C.\(_6^{14}C\)
D.\(_6^{14}B\)

A.Suppose that the Internet connection hadn't been stable, the teacher could conduct the online lesson successfully.
B.Without the stable Internet connection, the teacher could conduct the online lesson successfully.
C.If the Internet connection had been unstable, the teacher could have conducted the online lesson successfully.
D.But for the unstable Internet connection, the teacher could have conducted the online lesson successfully.

A.Suppose that the Internet connection hadn't been stable, the teacher could conduct the online lesson successfully.
B.Without the stable Internet connection, the teacher could conduct the online lesson successfully.
C.If the Internet connection had been unstable, the teacher could have conducted the online lesson successfully.
D.But for the unstable Internet connection, the teacher could have conducted the online lesson successfully.

A.Not until people are more concerned about online learning platforms has the COVID-19 resulted in schools shut all across the world.
B.Hardly had the Covid-19 result in schools shut all across the world when people are more concerned about online learning platforms.
C.Only after the COVID-19 has resulted in schools shut all across the world are people more concerned about online learning platforms.
D.Without people’s concern about online learning platforms, schools all across the world wouldn’t have been shut down.

A.\({q_1} > 0\) và \({q_2} < 0\)
B.\({q_1} < 0\) và \({q_2} > 0\)
C.\({q_1}.{q_2} > 0\)
D.\({q_1}{q_2} < 0\)

A.\({e_{tc}} =  - L\frac{{\Delta i}}{{\Delta t}}\)
B.\({e_{tc}} = 4\pi {.10^{ - 7}}{n^2}V\)
C.\({e_{tc}} = Li\)
D.\({e_{tc}} =  - L\frac{{\Delta t}}{{\Delta i}}\)

A.\(m\omega {A^2}.\)
B.\(\frac{1}{2}m\omega {A^2}.\)
C.\(m{\omega ^2}{A^2}.\)
D.\(\frac{1}{2}m{\omega ^2}{A^2}.\)

A.2 cm.
B.6 cm.
C.3 cm.
D.12 cm.