29.（ ）

(单选题)We can learn from the passage that ______. (单选题)What can we infer from Paragraph 2? (单选题)Why do people choose the evergreen tree for the Christmas tr (单选题)Hydrogen extracted from natural gas or coal is called ______ (单选题)Which of the following functions of hydrogen is not mentione (单选题)Which of the following is not among the main targets that sh (单选题)The goal of net-zero carbon emission is expected to be achie (单选题)Which of the following statement is false? (单选题)35.（   ） (单选题)34.（   ）