President johnson escalated american involvement in vietnam by
question 5 options:

declaring war.

having ngo dinh diem assassinated.

sending "advisers" to south vietnam.

ordering airstrikes and committing troops.

Correct  

Explanation:

After obtaining the Gulf of Tonkin resolution from Congress in 1964, President Lyndon Johnson escalated US involvement in the Vietnam war and magnified the number of US troops there by hundreds of thousands.  Between 1964 and the end of Johnson's presidency in 1969, US troop levels in Vietnam increased from around 20,000 to over 500,000.

Beginning in 1965, President Johnson also authorized an extensive program of airstrikes called Operation Rolling Thunder.  Over three years, from 1965 to 1968, Operation Rolling Thunder dropped over 600,000 tons of bombs on North Vietnam.

Read more about the Gulf of Tonkin resolution on -

a, c, & d are correct:

they wanted lands to settle the extra population.

they wanted new markets for english goods.

they wanted to avoid civil war.