The passage explains that Israel, as a newly developing state, found advantages in having an uncodified constitution that evolved through custom and statutes.
This makes Israel an example of a country without a formal single written constitution.
Option (a) People’s Republic of China — has a written constitution (1954) which, though nominal in practice, is still a formal document.
Option (b) Japan — has a concise written constitution, making this option incorrect.
Option (d) Indonesia — also has a short written constitution, so it does not fit the criteria of having no written constitution.
Thus, the correct example in the passage is Israel.