If plants and insects both existed for the first 300 million years after plants first evolved, why was pollination by insects not common in that period, as it is today?

• A. because insects at that time would not have been able to use nectar as food
• B. because insects were flightless at the time
• C. because plants were dominated by non-flowering plants at that time
• D. because nectars did not have a sweet taste at that time