Cyclosis (the streaming movement of cytoplasm within a cell) and amoeboid movements (the crawling-like movements of certain cells, such as amoebas and white blood cells) are primarily due to Microfilaments

Microfilaments, which are composed of actin protein subunits, are responsible for the contractile and movement-related activities within the cell. They play a key role in cellular processes involving changes in shape, cell motility, and the movement of organelles or materials within the cell. Cilia (Option B) are hair-like structures found on the cell surface and are primarily involved in cell locomotion and moving substances over the cell's surface. Microtubules (Option A) are involved in various cellular processes, including cell division and providing structural support. Intermediate filaments (Option D) provide structural support and are less involved in cellular movements compared to microfilaments.