If it is a checked form, put a tick or a cross in the box in front of the disease (fill in the form according to the instructions).
If it is declarative, please write down systemic diseases (such as coronary heart disease, diabetes, hyperthyroidism, etc. ), the insured has been diagnosed with major surgery or trauma (generally referred to as hospitalization).
You can consult an insurance broker when filling in the details.
Further reading: How to buy insurance, which is good, and teach you how to avoid these "pits" of insurance.