In the cells of some organisms, mitosis occurs without cytokinesis. this will result in
a. cells with more than one nucleus.
b. cells that are unusually small.
c. cells lacking nuclei.
d. cell cycles lacking an s phase

a. cells with more than one nucleus.

Explanation:

Mitosis is a cell division which completes in two stages. The first stage is called karyokinesis in which one nucleus divides into two and the second stage is called cytokinesis in which division of the cytoplasm takes place. During mitosis, cytokinesis is followed by karyokinesis. If a cell begins to divide and the division ceases after karyokinesis then the cell will have more then one nuclei in the absence of cytokinesis. Each of the  nuclei will have the same number of chromosomes.

A cell with more than one nucleus is called a multinucleated cell. For  example, human bone cell has many nuclei.