Answer:
b. spores of two types to spores of one type
Step-by-step explanation:
Spores of two types to spores of one type is not the trend to plant evolution because first the spores of one type is present in living organisms but with the passage of time evolution occurs that will leads to formation of spores of two types happen in living organisms. There are types of spores present in plants such as microspores, which produces male gametophytes, and megaspores, which produce female gametophytes while on the other hand, spores of one type is present in plants having asexual reproduction.