Which of the following finds row sums for each level of a grouping var

1.	Which of the following finds row sums for each level of a grouping variable?
A.	rowSums (x, na.rm = FALSE, dims = 1)
B.	colMeans(x, na.rm = FALSE, dims = 1)
C.	rowMeans(x, na.rm = FALSE, dims = 1)
D.	rowsum(x, group, reorder = TRUE, )
Answer» D. rowsum(x, group, reorder = TRUE, )

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