A) Hepatocellular carcinoma is a type of liver cancer and can be a complication of liver cirrhosis. However, it is not typically associated with difficulty sleeping or shortness of breath.

B) Portal hypertension, a common complication of liver cirrhosis, can lead to the development of ascites and esophageal varices, among other manifestations. It is not the likely cause of the client's difficulty sleeping and shortness of breath.

C) Hepatic encephalopathy is a neuropsychiatric complication of advanced liver disease and is not associated with difficulty sleeping or shortness of breath.

D) Hepatopulmonary syndrome is a complication of liver cirrhosis characterized by the development of pulmonary vascular dilation and arteriovenous shunting. This results in impaired oxygenation of blood, leading to difficulty breathing (dyspnea), especially while lying down (orthopnea). Clients with hepatopulmonary syndrome often experience frequent awakenings due to shortness of breath during sleep.