obligation

1.obligation（责任）后面可以接不定式，如our obligation to serve the people。

2.without obligation（不受约束地）和free and without obligation（免费而不受约束地）是商业常用语。例如：Call or write without obligation.（请亲自来或写信来询问都可以，问了不买也不妨。）和If you qualify under the simple rules, you will be given a complete preliminary home study course absolutely free and without obligation.