A common species of liverwort typically resembles a flat green ribbon that occasionally sprouts umbrella-shaped structures. If liverworts and mosses are very similar structurally, then the "ribbons" are and the "umbrellas" are .

1. Gametophyte

2. Sporophyte

Explanation:

The life cycle of the Liverwort and mosses which are placed in the Bryophytes is divided into the sporophytic and the gametophytic phase.

Gametophyte

The gametophyte is the dominant phase of the life cycle which appears like the ribbon, green in color and posses the gamete producing structure- the antheridium and the archegonium.  

Sporophyte

The gametes fuse to form the embryo and from that is produced the sporophyte structure, an umbrella-like structure called a sporangium. This sporangium produces the spores which later will form the gametophyte.

the answers are a and c

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!