If an S wave travels at 4 km/s to reach a seismic station 1200 km away, how much longer will secondary waves arrive after the primary waves?

Angiosperms are the most successful terrestrial plants. which of the following features is unique to them and account for their success? a. fruits enclosing seeds b. wind pollination c. sperm cells without flagella d. embryos enclosed within seed coats e. dominant gametophytes