When political researchers assess opinions towards President Bush's plan for social security reform, a(n) study is used. However, when political researchers want to assess the change in opinion towards the war in Iraq from the initial deployment of troops to the elections in Iraq, a(n) study should be used.

Awidower devised his fee simple interest in his residence as follows: “to my daughter for life, then to my oldest grandchild who survives her.” at the time of the widower’s death, he was survived by his only two children, a son and a daughter, and by one grandchild, his daughter’s son. a short time later, the daughter together with her son entered into a contract to sell the residence in fee simple to a buyer. the applicable jurisdiction continues to follow the common law rule against perpetuities, but has abrogated the rule in shelley’s case. at the closing, the buyer refused to purchase the residence. can the sellers compel the buyer to do so?