1. What does this "stock" refer to? "supply" or "a family(kind) of plants"?
2. The blank's answer is "in fact", can't "in short" work? "In short" also seems to work as it summarizes the idea of the previous parts.
st68)When people started to plant stored seed stock deliberately, they also began protecting their plants. This changed the evolutionary pressure that these food plants experienced, as they no longer had to survive in a natural environment....Thick, impermeable seed coats are often essential for seeds to survive in a natural environment, because the seeds of many wild plants remain dormant for months until winter is over and rain sets in. But under human management thick seed coats are unnecessary, as farmers take over responsibility for storing seeds away from moisture and predators.
_____, seeds with thinner coats were preferred as they are easier to eat or process, and they allow seedlings to sprout more quickly when sown.
Why not "in short", please?