The drug pyridostigmine is an acetylcholinesterase inhibitor that prevents the enzymatic breakdown of acetylcholine in synaptic clefts, including at neuromuscular junctions and parasympathetic post-ganglionic synapses.

Which of the following clinical conditions could this drug be used to treat?

1. Myasthenia gravis (an autoimmune disease causing skeletal muscle weakness due to the destruction of post-synaptic acetylcholine receptors)
2. Xerostomia (abnormally dry mouth caused by reduced salivary gland secretion)
3. Bradycardia (abnormally slow heart rate)