The least possible Venn diagram for the given statements is as follow:
Conclusions: I. No watch is a pendulum → False (As, watch and cell have direct relation but no direct relation with pendulum. So, the part of the cell that is pendulum is not watch and rest part of the pendulum is not considered).
II. No pendulum is a watch → False ( As only the part of the cell which is pendulum is not watch rest part have no relation)
III. Some pendulum are cells → True (As It clearly visible some part of cell are pendulum).
IV. All pendulum are cells → False (As Some part of the cell is pendulum but not all part is considered as pendulum)
Hence, "Only conclusion III follows".