54/100 spend less than two hours online each day.
42/100 spend between two and five hours online each day.
4/100 spend more than five hours online each day.
Although the third statement ("About 42% of the grandparents spend two or more hours online each day.") may seem right, the 4% that spend more than five hours online (which is also more than two) are ignored.
Therefore, the statement most likely to be true is the first ("About 46% of the grandparents spend two or more hours online each day.")