19. Which of the following expressions multiply the value of the integer variable $a by 4?

Вариант ответа 1 - A) $a *= pow (2, 2);

Вариант ответа 2 - B) $a >>= 2;

Вариант ответа 3 - C) $a <<= 2;

Вариант ответа 4 - D) $a += $a + $a;

Вариант ответа 5 - E) None of the above


Комментарий: The correct answers are A and C. In Answer A, the pow function is used to calculate 22, which corresponds to 4. In Answer C, the left bitwise shift operator is used to shift the value of $a by two bits to the left, which corresponds to a multiplication by 4.