V. Выберите правильную форму сказуемого

1. A similar method … to text for traces of petroleum gases dissolved in the seawater.

a) used; b) has been used; c) is used.

2. Gravity surveys … from the air.

a) carried out; b) are carried out; c) are carriage out.

3. Early wells … with impact-type tools.

a) was drilled; b) were drilled; c) drilled.