Correct Answer - D
The motion of the sphere is similar to projection motion.The components of its acceleration are `a_(x)=1.80m//s^(2),a_(y)=0`.When the sphere crosses the `y`-axis, its displacement component along `x`-axis is zero.`0=(v_(ix)t)+1/2a_(x)t_(2)`,
`0=3sin 30^(@)t-1/2(1.8)t^(2) or t=1.667 s`